Statistics Quiz 1
Response bias exists when
answers on survey do not reflect true feelings of respondent
To help assess student learning in her developmental physics course, a physics professor at a university implemented pre- and post- tests for her developmental physics students. A knowledge-gained score was obtained by taking the difference of the 2 test scores. What is the response variable in this experiment?
diff in test scores
Population
entire group being studied
Cohort study
first identifies group of individuals to participate in study [the cohort] observed over long period of time; characteristics about individuals are recorded and some individuals will be exposed to certain factors [not intentionally] and others will not
A closed question has
fixed choices for answers
open question is a
free-response question
descriptive statements
give info that is known
Determine the level of measurement of the variable year of birth of college students
interval
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What are the treatments?
300 mg of topiramate or placebo daily and weekly compliance enhancement intervention
A phlebotomist draws the blood of a random sample of 50 patients and determines their blood types as shown. Use the results of the sample to conjecture the percentage of the population that has type O blood. Is this an example of descriptive or inferential statistics? relative frequency .38
38%; inferential
Variables
characteristics of individuals within population
Consider the following question from a recent poll: Thinking about how the nuclear proliferation issue might affect your vote for major offices, would you vote only for a candidate who shares your views on nuclear proliferation or consider a candidates position on nuclear proliferation as just one of many important factors? [rotated] Why is it important to rotate the two choices presented in the question?
choices need to be rotated to minimize response bias
in a pie chart
percentages must add up to 100
A web page design firm has 2 designs for an online hardware store. To determine which is the more effective design, the firm uses one page in the Denver area and a second page in the Oakland area. For each visit, the firm records the amount spent by the visitor and the number of items viewed. What are the 2 response variables? Qualtitative or quantitative?
1 response variable is amount spent by visitor; quantitative 1 response variable is number of items viewed; quantitative
A pharmaceutical company wants to conduct a survey of 30 individuals who have high cholesterol. The company has obtained a list from primary care physicians throughout the country of 5100 individuals who are known to have high cholesterol. Design a sampling method to obtain individuals in sample
1) group individuals by common primary care physician. Assign each physsician diff number and use random number table to select physicians until total number pts of all selected physicians is at least 30 2) Alphabetize list of 5100 individuals by last name and select one of first 170 individuals at random. Starting from selected invidiaul, read down list and select every 170th individual 3) Group individuals by common primary care physician. For each group, assign all individuals diff numbers and use random number table to select appropriate number individuals
Suppose you are the president of the student government. You wish to conduct a survey to determine the student body's opinion regarding student services. The administration provides you with a list of the names and phone numbers of the 648 registered students. Random number table: 82398, 97945 56142, 07432 96829, 01924 92072, 85625 04927, 10341 22543, 60577 41497, 89364 23485, 87472 23621, 50774 66898, 48655 What are some procedures you could follow to obtain a simple random sample of 5 students?
1) list each name on separate piece of paper, place them all in a hat & pick 5 2) number names from 1-648 and use random number table to produce 5 diff 3 digit numbers corresponding to names selected
As part of a college literature course, students must read 3 classic works of literature from the provided list. Write a short description of the processes that can be used to generate a simple random sample of 3 books. Obtain a simple random sample of size 3 from this list. Which of the following would produce a simple random sample? Select all that apply.
1) number books from 1-9 and use random number generator to produce 3 diff numbers from 1-9 that correspond to books selected 2) list each book on separate piece of paper, place them all in hat and pick 3
A club wants to sponsor a panel discussion on the upcoming national election. The club wants 4 of its members to lead the panel discussion. Write a short description of the processes that can be used to generate your sample. Obtain a simple random sample of size 4 from the table. Which of the following would produce a simple random sample?
1) number names from 1-25 and use random number generator to produce 4 diff numbers corresponding to names 2) list each name on separate piece of pape, place them all in hat & pick 4
What are some solutions to nonresponse bias?
1) offer rewards and incentives 2) attempt callbacks
Suppose that a newspaper predicted that candidate A would defeat Candidate B in a certain election. They conducted a poll of home owners with a response rate of 24%. On the basis of the results, the newspaper predicted that Candidate A would win with 57% of the popular vote. However, candidate B won the election with about 62% of the popular vote. At the time of this poll, most home owners belonged to the party of candidate A. Name 2 biases that led to this incorrect prediction
1) sampling bias: using incorrect frame led to undercoverage 2) nonresponse bias: low response rate caused bias
A salesperson obtained a systematic sample of size 25 from a list of 500 clients. To do so, he randomly selected a number from 1 to 20, obtaining the number 12. He included in the sample the 12th client on the list and every 20th client thereafter. List the numbers that correspond to the 25 clients selected.
12, 32..., 492
A community college has 7657 students currently enrolled in classes. To gain the students' opinions about an upcoming building project, the college president wishes to obtain a simple random sample of 8 students. He numbers the students from 1 to 7657. Random number table: Row 1: 93901, 31469, 17219, 23124 Row 2: 36618, 95809, 08783, 19824 Row 3: 11295, 11384, 35908, 39112 Row 4: 95155, 13751, 03640, 32817 Row 5: 91512, 48073, 51653, 35158 Row 6: 04176, 05327, 34367, 00805 Using the provided random number table, the president closes his eyes and drops his ink pen on the table. It points to the digit in row 2, column 4. Using this position as the starting point and proceeding downwrad, determine the numbers for the 8 students who will be included in the sample.
1895, 5513, 1248, 7605, 4691, 3843, 7510, 0735
Suppose you are the president of the student government. You wish to conduct a survey to determine the student body's opinion regarding student services. The administration provides you with a list of the names and phone numbers of the 648 registered students. Random number table: 82398, 97945 56142, 07432 96829, 01924 92072, 85625 04927, 10341 22543, 60577 41497, 89364 23485, 87472 23621, 50774 66898, 48655 Obtain this sample using the portion of the random number table provided in the problem statement. Start with the first column of the first row and work down each column
561, 049, 225, 414, 234
A community college has 7657 students currently enrolled in classes. To gain the students' opinions about an upcoming building project, the college president wishes to obtain a simple random sample of 8 students. He numbers the students from 1 to 7657. Random number table: Row 1: 93901, 31469, 17219, 23124 Row 2: 36618, 95809, 08783, 19824 Row 3: 11295, 11384, 35908, 39112 Row 4: 95155, 13751, 03640, 32817 Row 5: 91512, 48073, 51653, 35158 Row 6: 04176, 05327, 34367, 00805 The president uses technology to produce the following random numbers. Determine the numbers for 8 students who will be included in the sample 6710, 4682, 214, 4623, 1790, 4682, 5109, 5062, 3025, 214
6710, 4682, 214, 4623, 1790, 5109, 5062, 3025
A study conducted by researchers was designed "to determine if application of duct tape is as effective as cryotherapy in the treatment of common warts." The researchers randomly divided 60 patients into 2 groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were complete, it was determined that 73% of the patients in group 1 and 90% of the patients in group 2 had complete resolution of their warts. The researchers concluded that cryotherapy is significantly more effective in treating warts than duct tape. what are the descriptive statistics?
73% of patients in group 1 and 90% of patients in group 2 had resolution of their warts
A community college employs 86 full-time faculty members. To gain the faculty's opinions about an upcoming building project, the college president wishes to obtain a simple random sample that will consist of 9 faculty members. He numbers the faculty from 1 to 86. Using the provided random number table, the president closes his eyes and drops his ink pen on the table. It points to the digit in row 3, column 6. Using this position as the starting point and proceeding downward, determine the numbers for the 9 faculty members who will be included in the sample. Random number table: Row 1: 58992, 15104, 44060, 31725 Row 2: 39986, 64841, 57392, 66508 Row 3: 11848, 99187, 54907, 95275 Row 4: 56977, 78439, 39809, 09639 Row 5: 42540, 57918, 75648, 27537 Row 6: 06923, 89633, 37030, 15563
78, 57, 10, 84, 18, 43, 63, 44, 15
The manager of a shopping mall wishes to expand the number of shops available in the food court. He has a market researcher survey the first 90 customers who come into the food court during weekday afternoons to determine what types of food the shoppers would like to see added to the food court. Suggest a remedy to the problem.
Ask customers throughout day on both weekdays and weekends
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. What is the research question the study addresses?
Does season of birth affect mood?
True or false. A simple random sample is always preferred because it obtains the same information as other sampling plans but requires a smaller sample size.
False bc other sampling techniques may provide more info for less cost than simple random sample
True or false: In statistics, results are always reported with 100% certainty.
False. In stats, results are not reported w 100% certainty. Bc statistical studies draw on samples & bc there is variation within groups, results cannot be reported w 100% certainty
True or false: Statistical studies are not concerned with understanding the sources of variability in data, only with describing the variability in the data.
False. Statistical studies are concerned w both describing variability in data & understanding sources of variability in data. Understanding sources allows researchers to control it & reach better conclusions
True or false. When obtaining a stratified sample, the number of individuals included within each stratum must be equal.
False. Within stratified samples, number of individuals sampled from each stratum should be proportional to size of strata in population
To help assess student learning in her developmental physics course, a physics professor at a university implemented pre- and post- tests for her developmental physics students. A knowledge-gained score was obtained by taking the difference of the 2 test scores. What type of experimental design is this?
Matched pair
Suppose you are interested in comparing brand A exterior latex paint to brand B exterior latex paint. Design an experiment to determine which paint is better for painting siding
Matched-pairs design bc experimental units are paired up & there are only 2 levels of treatment.
A student entering a doctoral program in education psychology is required to select two courses from the list of courses provided as part of his or her program. All of the possible two course selections are: 1) 636, 650 2) 606, 666 3) 606, 634 4) 666, 650 5) 634, 691 6) 691, 650 7) 634, 666 8) 666, 691 9) 606, 650 10) 606, 691 Comment on the likelihood that EPR 666 and EPR 650 will be selected.
There is 1 in 10 chance that these courses will be selected
True or false. Inferences based on voltunary response samples are generally not reliable.
True bc often individuals who volunteer do not accuraetly represent population
True or false: Suppose 3 different individuals conduct the same statistical study, such as estimating the average commute time of students at a college. It is possible that all 3 studies end up with different results.
True. Statistical studies typically look at samples rather than entire populations. Since each study is likely to draw diff samples, it is quite possible that each study ends up w diff results due to variability in data
A poll is being conducted at a sporting event to obtain a sample of the population of an entire country. What is the frame for this type of sampling? Who would be excluded from the survey and how might this affect the results of the survey? What is the frame for this time of survey?
entire population of country
Consider these two questions: 1) What is the most important problem facing the nation? 2) Do you approve or disapprove of the way the president is handling his job? Will the order in which the questions are asked affect the survey results? If so, what can the pollster do to alleviate this response bias?
Yes, question order will affect survey results Pollster should alternate order of questions given in questionnaire so diff respondents receive questionnaire with same questions but diff question orderings
A value of zero in the ratio level of measurement means
absence of quantity Arithmetic opreations such as multiplication and division can be performed on values of variable
How to calculate relative frequency
add all frequencies together to get total number then divide frequency of each category by total number respondents
A quality-control manager randomly selects 70 bottles of tomato sauce that were filled on November 22 to assess the calibration of the filling machine What is the population in the study?
all bottles of tomato sauce produced in the plant on november 22
frame
all individuals within population
Researchers wanted to test the effectiveness of a new drug therapy for treating patients with colon cancer. to do this, they identified 90 patients with a diagnosis of colon cancer. Patients were randomly assigned to one of three treatment groups. 30 patients were randomly assigned to receive the new drug therapy, another 30 received the older drug therapy and the final 30 received a placebo therapy. To measure the effectiveness of the treatment, researchers scored each patient on a standardized rating scale for colon cancer. After collecting and comparing the scores for the 3 treatment groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of colon cancer. What is the population being studied?
all patients w diagnosis of colon cancer
To determine customer opinion of their food quality, General Foods randomly selects 30 city blocks during a certain week and surveys all homes within the city blocks. What type of sampling is used?
cluster
What sampling methods require a frame?
cluster, stratified, simple random
Researchers wanted to determine if there was an association between the level of satisfaction of an individual and their risk of high blood pressure. The researchers studied 1519 people over the course of 12 years. During this 12 year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of high blood pressure over the 12 year period. After their analysis, the researchers concluded that the satisfied individuals were less likely to experience high blood pressure. What type of observational study was this? Explain.
cohort study bc info was collected about group of individuals by observing them over long period of time
Value of zero in interval level of measurement
does not mean absence of quantity arithmetic operations such as addition and subtraction can be performed on values of variable
Completely randomized design
each experimental unit is radnomly assigned to a treatment
Advantages and disadvantages of closed questions
easier to analyze but limit responses
confounding
effect of 2 factors [explanatory variables on response variable] cannot be distinguished.
Confounding in a study occurs when
effects of 2 or more explanatory variables are not separated.
If the voting issue is a national one. To obtain a good representation of the entire population, the sampling method should
ensure coverage of multiple geographic locations bc interests of group of people in country tend be more alike when looked at geographically.
Table: Setup: ABCDE Size (in): 58, 59, 56, 42, 43 Screen type: Projection, projection, plasma, plasma, plasma Number of type channels available: 299, 113, 425, 269, 289 What are the individuals being studied?
high-definition television setups A-E
What is a bar graph?
horizontal or vertical representation of frequency or relative frequency of categories height of each rectangle represents category's frequency of relative frequency
For voluntary response
individuals who decide to be in sample generally have strong opinions about topic.
A national survey asked people, "How often do you eat out for dinner, instead of at home?" The frequencies were as follows. Suppose a person claims that, "2.62.6% of all people in the nation always eat out." Is this a descriptive or inferential statement?
inferential
placebo
innocuous medication, such as sugar tablet, that looks, tastes, and smells like experimental medication
Determine the level of measurement of the variable years of elections: 1988, 1992, 1996, 2000 and 2004
interval
Nonsampling error occurs because
process of obtaining data
A variable is at the ratio level of measurement if it has
properties of interval level of measurement and ratios of values of variable have meaning
A variable is at the interval level of measurement if it has
properties of ordinal level of measurement & diffs in values of variable have meaning
What does it mean when an observational study is prospective?
prospective study collects data over time.
Statistics is also about
providing measure of confidence in any conclusions
Determine whether the variable is qualitative or quantitative Favorite basketball player
qualitative bc attribute characteristic
Determine whether the variable is qualitative or quantitative Favorite musical instrument
qualitative bc attribute characteristic
Determine whether the variable is qualitative or quantitative Medal won in race
qualitative bc attribute characteristic
Table: Setup: ABCDE Size (in): 58, 59, 56, 42, 43 Screen type: Projection, projection, plasma, plasma, plasma Number of type channels available: 299, 113, 425, 269, 289 Determine whether each variable is qualitative, continuous or discrete Screen type is a
qualitative variable
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. What type of variable is the season in which you were born?
qualitative, nominal
Determine whether the variable is qualitative or quantitative Number of words in a speech
quantitative bc numerical measure
response variable
quantitative or qualitative variable for which experimenter wishes to determine how its value is affected by explanatory variable
In a relative frequency distribution, what should the relative frequencies add up to?
relative frequencies should add up to 1
What is a designed experiment?
researcher assigns individuals to certain group, intentionally changing value of explanatory variable & then recording value of response variable for each group
With statistics,
results should be reported w some measure that represents how convinced we are that conclusions reflect reality
What does it mean when an observational study is retrospective?
retrospective study requires that individuals look back in time or require researcher to look at existing records.
Sampling error occurs because
sample gives incomplete info about population
A retail manager wants to conduct a study regarding the shopping habits of his customers. He selects the first 60 customers who enter his store on a Saturday morning. What is the type of bias?
sampling bias
The manager of a shopping mall wishes to expand the number of shops available in the food court. He has a market researcher survey the first 90 customers who come into the food court during weekday afternoons to determine what types of food the shoppers would like to see added to the food court. What is the cause of the bias?
sampling bias
For looking at a national voting issue
sampling method should keep sample sizes as small as possible.
Statistics
science of collecting, organizing, summarizing & analyzing info to draw conclusion & answer questions
Researchers wanted to test the effectiveness of a new drug therapy for treating patients with colon cancer. to do this, they identified 90 patients with a diagnosis of colon cancer. Patients were randomly assigned to one of three treatment groups. 30 patients were randomly assigned to receive the new drug therapy, another 30 received the older drug therapy and the final 30 received a placebo therapy. To measure the effectiveness of the treatment, researchers scored each patient on a standardized rating scale for colon cancer. After collecting and comparing the scores for the 3 treatment groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of colon cancer. What is the response variable in this study?
score on standardized rating scale for colon cancer
A quality-control manager randomly selects 70 bottles of tomato sauce that were filled on November 22 to assess the calibration of the filling machine What is the sample in the study?
the 70 bottles of tomato sauce selected in plant on november 22
A person's age
will change over time.
Similar individuals
will not necessarily yield same data people can be diff heights, weights, ages etc
It is extremely important for a researcher to clearly define the variables in a study because this helps to determine the type of analysis that can be performed on the data. For example, if a researcher wanted to describe hockey players based on jersey number, what level of measurement would the variable jersy number be? Now suppose the researcher felt that certain players who were older received higher numbers. Does the level of measurement of the variable change? If so, how? Does the level of measurement change in the second scenario?
yes it changes to ordinal
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. Can you think of any lurking variables that may affect the results of the study?
yes like drinking habits and amount of exercise per week
Suppose a surveyor wants to conduct a phone survey about a new movie. He plans to take a simple random sample. However, some people are not at home. Do you believe this can affect the ability of the surveyor to obtain accurate polling results? If so, how?
yes, esp if people not at home have trait that is not accurately represented by remaining people in sample
Confounding is potentially a major problem with
observational studies.
factor
variable whose effect on response variable is to be assessed by experimenter
A community college employs 86 full-time faculty members. To gain the faculty's opinions about an upcoming building project, the college president wishes to obtain a simple random sample that will consist of 9 faculty members. He numbers the faculty from 1 to 86. Using the provided random number table, the president closes his eyes and drops his ink pen on the table. Random number table: Row 1: 58992, 15104, 44060, 31725 Row 2: 39986, 64841, 57392, 66508 Row 3: 11848, 99187, 54907, 95275 Row 4: 56977, 78439, 39809, 09639 Row 5: 42540, 57918, 75648, 27537 Row 6: 06923, 89633, 37030, 15563 The president uses technology to produce the following random numbers. Determine the numbers for 9 faculty members who will be included in the sample. 81, 68, 22, 24, 57, 68, 11, 27, 66, 65
81, 68, 22, 24, 57, 11, 27, 66, 65
The human resource department at a certain company wants to conduct a survey regarding worker benefits. The department has an alphabetical list of all 3928 employees at the company and wants to conduct a systematic sample of size 40. Determine the individuals who will be administered in the survey. Randomly select a number from 1 to k. Suppose that we randomly select 9. Starting with the first individual selected, the individuals in the survey will be:
9, 107, 205..., 3831
The human resource department at a certain company wants to conduct a survey regarding worker benefits. The department has an alphabetical list of all 3928 employees at the company and wants to conduct a systematic sample of size 40. What is k?
98
Surveys tend to suffer from low response rates. Based on past experience, a researcher determines that the typical response rate for an email survey is 30%. She wishes to obtain a sample of 225 respondents so she emails the survey to 1500 randomly selected email addresses. Assuming the response rate for her survey is 30%, will the respondents form an unbiased sample? Explain.
No. Survey still suffers from undercoverage [sampling bias], nonresponse bias and potentially response bias
A club wants to sponsor a panel discussion on an upcoming election. The club wants to have four of its members lead the panel discussion. To be fair, however, the panel should consist of two members of each party. Below is a list of members in each party. Obtain a stratified sample of two people from party 1 and two from party 2. Party 1: Bolden, Carter, Haydra, Lukens; Nolan, Pawlak, Tate, Wright Party 2: Cooper, Engler, Keating, May; Ochs, Rice, Thomas, Weber Which is a possible list of club members to lead the discussion? 1) Keating, May, Cooper, Rice 2) Nolan, Carter, Haydra, Keating 3) Nolan, Carter, Keating, May 4) Nolan, Carter, Haydra, Bolden 5) Keating, May, Cooper, Nolan
Nolan, Carter, Keating, May
A club wants to sponsor a panel discussion on the upcoming national election. The club wants 4 of its members to lead the panel discussion. Club membership list: 1) Blouin 2) Bolden 3) Bolt 4) Carter 5) Cooper 6) Debold 7) Engler 8) Grajewski 9) Hayes 10) Hamilton 11) Keating 12) Lukens 13) May 14) Motola 15) Nolan 16) Ochs 17) Pawlak 18) Ramirez 19) Rice 20) Tate 21) Thompson 22) Washington 23) Williams 24) Wright 25) Zenkel The list of digits below is from a random number generator using technology. Use the list of numbers to obtain a simple random sample of size 4 from this list. If you start with the first number in the list and take the first 4 numbers between 1 and 25, what 4 members would be selected from the numbered list? 15, 7, 15, 23, 7, 18, 25, 20, 7, 2, 25, 16, 4, 23, 11
Nolan, Engler, Williams, Ramirez
Determine the level of measurement of the variable Ranks of scores in a tournament
Ordinal
Determined whether the underlined numerical value is a parameter or a statistic. Explain. Two students out of all 29 students in a class have red hair
Parameter bc data set of all 29 students is a population
Using rewards and incentives is another method to improve nonresponse.
Rewardslike cash payments. Incentives like cover letter that states that responses to questionnaire will determine future policy.
Explain what is meant when it is said that "data vary." How does the variability affect the results of statistical analysis?
Saying "data vary" means values of variable change from individual to individual in addition, certain variables can change over time for certain individuals bc data can vary, 2 diff statistical analysis of same variable can lead to diff results
A web page design firm has 2 designs for an online hardware store. To determine which is the more effective design, the firm uses one page in the Denver area and a second page in the Oakland area. For each visit, the firm records the amount spent by the visitor and the number of items viewed. Explain how confounding might be an issue with this study.
Since designs are being tested w 2 diff locations, preferences depending on location may affect response variables for those groups.
As part of a college literature course, students must read 3 classic works of literature from the provided list. Write a short description of the processes that can be used to generate a simple random sample of 3 books. Obtain a simple random sample of size 3 from this list. The list of digits below is from a random number generator using technology. USe the list of numbers to obtain a simple random sample of size 3 from list list. If you start on the left and take the first 3 numbers between 1 and 9, what 3 books would be selected from the numbered list? 1, 6, 1, 0, 1, 4, 6, 0, 9, 0, 3, 5, 5, 8, 8 1) The Jungle 2) As I Lay Dying 3) The Sun Also Rises 4) Pride and Prejudice 5) Death of a Salesman 6) Huckleberry Finn 7) Crime and Punishment 8) A Tale of Two Cities 9) The Scarlet Letter
The Jungle, Huckleberry Finn, Pride and Prejudice
Parameter
numerical summary of population
A study conducted by researchers was designed "to determine if application of duct tape is as effective as cryotherapy in the treatment of common warts." The researchers randomly divided 60 patients into 2 groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were complete, it was determined that 73% of the patients in group 1 and 90% of the patients in group 2 had complete resolution of their warts. The researchers concluded that cryotherapy is significantly more effective in treating warts than duct tape. what is the population being studied?
all people who have warts
Advantages and disadvantages of open questions
allow respondents to state exactly how feel but harder to analyze due to variety of answers & possible misinterpretation of answers
treatment
any combination of values of factors [explanatory variables]
A poll is being conducted at a sporting event to obtain a sample of the population of an entire country. What is the frame for this type of sampling? Who would be excluded from the survey and how might this affect the results of the survey? Who would be excluded from the survey and how might this affect the results of the survey?
any person who does not enjoy watching sporting events is excluded; can result in sampling bias due to undercoverage
Confounding result
any relation that may exist between explanatory variable & response variable may be due to some other variable(s) not accounted for in study.
What is replication in an experiment?
applying each treatment to more than one experimental unit
What is a pareto chart?
bar graph whose bars are drawn in decreasing order of frequency or relative frequency
Sampling error is the error that results
bc sample is being used to estimate info about population
If nonresponse occurs because an individual was not at home,
callback might mean returning to home at other times in day or on other days of week.
Nonresponse bias can be controlled using
callbacks.
height and weight
can change over time
Measuring 2 people's heights at same time or measuring one person's height at diff times
can yield diff results
A statistic is
numerical summary of sample
Researchers wanted to test the effectiveness of a new drug therapy for treating patients with colon cancer. to do this, they identified 90 patients with a diagnosis of colon cancer. Patients were randomly assigned to one of three treatment groups. 30 patients were randomly assigned to receive the new drug therapy, another 30 received the older drug therapy and the final 30 received a placebo therapy. To measure the effectiveness of the treatment, researchers scored each patient on a standardized rating scale for colon cancer. After collecting and comparing the scores for the 3 treatment groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of colon cancer. What type of experimental design is this?
completely randomized design
Descriptive statistics
consists of organizing & summarizing info collected
Table: Setup: ABCDE Size (in): 58, 59, 56, 42, 43 Screen type: Projection, projection, plasma, plasma, plasma Number of type channels available: 299, 113, 425, 269, 289 Determine whether each variable is qualitative, continuous or discrete Size is a
continuous variable
A designed experiment involves
controlling value of explanatory value to see effect on response variable
A magazine asks its readers to call in their opinion regarding the quality of the articles. What type of sampling is used?
convenience
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. What type of observational study is this?
cross-sectional study
Researchers wanted to determine if there was an association between daily coffee consumption and the occurence of heart disease. The researchers looked at 93, 933 women and asked them to report their coffee-drinking habits. The researchers also determined which of the women had congestive heart failure. After their analysis, the researchers concluded that consumption of 6 or more cups of caffeinated coffee per day was associated with a reduction in congestive heart failure. What type of observational study was this? Explain
cross-sectional study bc all info about individuals was collected at specific point in time
A study conducted by researchers was designed "to determine if application of duct tape is as effective as cryotherapy in the treatment of common warts." The researchers randomly divided 60 patients into 2 groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were complete, it was determined that 73% of the patients in group 1 and 90% of the patients in group 2 had complete resolution of their warts. The researchers concluded that cryotherapy is significantly more effective in treating warts than duct tape. What is the conclusion of the study?
cryotherapy is significantly more effective than duct tape in treating warts
Which allows the researcher to claim causation between an explanatory variable and a response variable?
designed experiment
In statistical studies, researchers want to
determine how varying one or more explanatory variables may impact value of response variable
What can cause under-representation
diff types of bias or even random chance
Determine whether the quantitative variable is discrete or continuous number of bacteria seen on microscope slide
discrete bc countable
Determine whether the quantitative variable is discrete or continuous number of beats in a song
discrete bc countable
Determine whether the quantitative variable is discrete or continuous number of points scored in a baseball game
discrete bc countable
Determine whether the quantitative variable is discrete or continuous number of words in a poem
discrete bc countable
Table: Setup: ABCDE Size (in): 58, 59, 56, 42, 43 Screen type: Projection, projection, plasma, plasma, plasma Number of type channels available: 299, 113, 425, 269, 289 Determine whether each variable is qualitative, continuous or discrete Number of channels available is a
discrete variable
Determine whether the study depicts an observational study or an experiment. First-grade students are randomly divided into 2 groups. One group is given a fruit and vegetable for lunch; the other is given candy for lunch. After lunch, each group is given an attention test to comapre hyperactivity.
experiment bc reearchers control one variable to determine effect on response variable
Determine whether the study depicts an observational study or an experiment. 8th grade students are randomly divided into 2 groups. One group is taught math using traditional techniques. The other is taught math using a reform method. After 1 year, each group is given an achievement test to compare its proficiency with that of the other group.
experiment bc researchers control one variable to determine effect on response variable
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be placebo-controlled?
experiment will have control group that takes placebo [innocuous medication like sugar tablet] to serve as baseline treatment that can be used to compare group that actually takes medication
Matched-pairs design
experimental design in which experimental units are paired up
Randomized block design
experimental units divided into homogenous groups called blocks
Researchers wanted to determine if there was an association between daily coffee consumption and the occurence of heart disease. The researchers looked at 93, 933 women and asked them to report their coffee-drinking habits. The researchers also determined which of the women had congestive heart failure. After their analysis, the researchers concluded that consumption of 6 or more cups of caffeinated coffee per day was associated with a reduction in congestive heart failure. What is the explanatory variable?
explanatory variable is consumption of caffeinated coffee
A web page design firm has 2 designs for an online hardware store. To determine which is the more effective design, the firm uses one page in the Denver area and a second page in the Oakland area. For each visit, the firm records the amount spent by the visitor and the number of items viewed. What is the explanatory variable in this study? Is it qualitative or quantitative?
explanatory variable is web page design; qualitative
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. What is the explanatory variable?
explanatory variable is whether adolescent has supply of sugary snacks in bedroom or not
A confounding variable is
explanatory variable that was considered in study whose effect cannot be distinguished from second explanatory variable in study.
A lurking variable is
explanatory variable that was not considered in study, but that affects value of response variable in study.
A gambler wanted to compare 2 types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the 2 types of strategy. What is the factor that is set to predetermined levels? What is the treatment?
factor is type of strategy; treatments are playing tight and loose style of play
True or false. When taking a systematic random sample of size n, every group of size n from the population has the same chance of being selected
false bc certain groups would never be selected
true or false When a factor is controlled by setting it to three levels, the particular factor is of no interest to the researcher.
false bc factor that is controlled and set at various levels is factor of interest to researcher.
A variable is at the ordinal level of measurement if
has properties of nominal level of measurement & naming scheme allows for values of variable to be arranged in ranked or specific order
An anti-smoking advocate wants to estimate the percentage of people who favor decreasing the use of advertising to sell cigarettes. She conducts a nationwide survey of 1070 randomly selected adults 18 years and older. The interviewer asks the respondents "Do you favor higher health insurance premiums for smokers?" How can the bias be remedied?
interviewer should reword question
What does it mean when a part of the population is under-represented?
it is proportionally smaller in sample than in its population
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. People born in spring are
less likely to be depressive
Researchers wanted to determine if there was an association between the level of satisfaction of an individual and their risk of high blood pressure. The researchers studied 1519 people over the course of 12 years. During this 12 year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of high blood pressure over the 12 year period. After their analysis, the researchers concluded that the satisfied individuals were less likely to experience high blood pressure. What is the explanatory variable and why?
level of satisfaction bc it affects other variable
A frequency distribution
lists number of occurences of each category of data
Relative frequency distribution
lists proportion of occurences of each category of data
Often, the cause of confounding is
lurking variable.
A relation that appears to exist between a certain explanatory variable and the response variable may be due to some other variable or variables not accounted for in the study.
lurking variables
The big difference between lurking variables and confounding variables is that
lurking variables are not considered in study whereas confounding variables are measured in study.
A gambler wanted to compare 2 types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the 2 types of strategy.
matched-pairs design
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be randomized?
means subjects are randomly assigned to take either topiramate or placebo
What is an observational study?
measures value of response variable without attempting to influence value of either response or explanatory variables.
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. People born in autumn are
more likely to have mood swings
how to find percentage of relative frequency
multiply decimal by 100
double-blind experiment
neither subject nor researcher in contact w subject knows which treatment is received.
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What does it mean for the experiment to be double-blind? Why do you think it is necessary for the experiment to be double-blind?
neither subject nor researcher knows which treatment subject is receiving so subjects receiving meds do not behave diff and individual monitoring subjects does not treat med subjects diff than those receiving placebo
Researchers wanted to test the effectiveness of a new drug therapy for treating patients with colon cancer. to do this, they identified 90 patients with a diagnosis of colon cancer. Patients were randomly assigned to one of three treatment groups. 30 patients were randomly assigned to receive the new drug therapy, another 30 received the older drug therapy and the final 30 received a placebo therapy. To measure the effectiveness of the treatment, researchers scored each patient on a standardized rating scale for colon cancer. After collecting and comparing the scores for the 3 treatment groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of colon cancer. What are the treatments?
new drug therapy, older drug therapy and placebo drug therapy
Researchers wanted to know if there is a link between proximity to high-tension wires and the rate of leukemia in children. To conduct the study, researchers compared the rate of leukemia for children who lived within 1/2 mile of high-tension wires to the rate of leukemia for children who did not live within 1/2 mile of high-tension wires. The researchers found that the rate of leukemia for children near high-tension wires was higher than the rate for those not near high-tension wires. Can the researchers conclude that proximity with high-tension wires causes leukemia in children?
no bc this is observational study
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. Does a supply of sugary snacks in the bedroom cause a higher body mass index? Explain.
no. it can only be said that supply of sugary snacks in bedroom and obesity are associated bc body mass index of adolescents who had supply of sugary snacks in bedroom was significantly higher than that of adolescents who did not have supply of sugary snacks in bedroom
Determine the level of measurement of the variable eye color
nominal
It is extremely important for a researcher to clearly define the variables in a study because this helps to determine the type of analysis that can be performed on the data. For example, if a researcher wanted to describe hockey players based on jersey number, what level of measurement would the variable jersy number be? Now suppose the researcher felt that certain players who were older received higher numbers. Does the level of measurement of the variable change? If so, how? What is the level of measurement of the variable jersey number in the original scenario?
nominal
A polling organization conducts a study to estimate the percentage of households that have pets. It mails a questionnaire to 1524 randomly selected households across the country and asks the head of each household if he or she has pets. Of the 1524 households selected, 20 responded. Which of these best describes the bias in the survey?
nonresponse bias
During every election in a particular region, pollsters conduct exit polls to determine which candidate people voted for. During the most recent election, pollsters incorrectly predicted candidate A the winner over candidate B. When asked how this error could have happened, the pollsters cited error due to the fact that since many of the interviewers were older, only older voters were selected in the sample agreed to be interviewed and older voters tended to favor candidate A. In addition, the method of selecting individuals to be interviewed led to selecting a higher proportion of female voters and candidate A was favored by females. Explain which nonsampling errors led to the incorrect conclusion regarding the election
nonresponse bias is nonsampling error that contributed to incorrect conclusion bc individuals who were selected for polling but did not respond voted diff than those who did respond to polling
A gambler wanted to compare 2 types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the 2 types of strategy. What is the response variable in this study?
number of pots won
Determine whether the study depicts an observational study or an experiment. A study is conducted to determine if there is a relationship between height and childhood exposure to measles. Students have their height measured and are asked about childhood exposure to measles.
observational study bc study examines individuals in sample but does not try to influence response variable
Replication helps to show
observed effects are not due to some characteristic of single experimental unit but instead due to treatment
In an observational study, the researcher
observes behavior of individuals without trying to influence outcome of study
Cluster sample
obtained by dividing population into groups & selecting all individuals from within random sample of groups
Stratified sample
obtained by dividing population into homogenous groups & randomly selecting individuals from each group
Systematic sample
obtained by selecting every kth individual from population
What does it mean when sampling is done without replacement?
once individual is selected, individual cannot be selected again
When sampling without replacement,
once individual is selected, individual is removed from possible choices for that sample and cannot be chosen again
Determine the level of measurement of the variable Highest degree conferred [high school, bachelor's & so on]
ordinal
Determined whether the underlined numerical value is a parameter or a statistic. Explain. Following the election, 18% of the governors of all 50 areas of a country were female
parameter bc governors of all 50 area of a country are a population
Discuss a possible disadvantage of offering rewards or incentives to increase response rates.
people interested in rewards or incentives differ from population in some way that is important to study, causing biased results
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What is the response variable?
percentage of heavy drinking days
experimental unit
person, object, or some other well-defined item upon which treatment is applied
if nonresponse occurs because a mailed questionnaire was not returned, a callback might mean
phoning individual to conduct survey.
To help assess student learning in her developmental physics course, a physics professor at a university implemented pre- and post- tests for her developmental physics students. A knowledge-gained score was obtained by taking the difference of the 2 test scores. What is the treatment?
physics course
A gambler wanted to compare 2 types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the 2 types of strategy. Identify the experimental units
poker players
A polling organization conducts a study to estimate the percentage of households that have pets. It mails a questionnaire to 1524 randomly selected households across the country and asks the head of each household if he or she has pets. Of the 1524 households selected, 20 responded. How can the bias be remedied?
polling organization should try contacting households that do not respond by phone or face to face
To determine if topiramate is an effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this doubleblind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. What is the population for which this study applies? What is the sample?
population is all 18-65 year olds with alcohol dependence. Sample is 371 men and women aged 18-65 diagnosed with alcohol dependence
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. Why is this an observational study?
researchers administered a questionnaire to obtain data without trying to influence an explanatory variable of study
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. In the report, the researchers stated "these results remain significant after adjustment for socioeconomic status." What does this mean?
researchers made an effort to avoid confounding by accounting for potential lurking variables
Researchers wanted to determine if there was an association between the level of satisfaction of an individual and their risk of high blood pressure. The researchers studied 1519 people over the course of 12 years. During this 12 year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of high blood pressure over the 12 year period. After their analysis, the researchers concluded that the satisfied individuals were less likely to experience high blood pressure. In the report, the researchers stated that "the research team also hasn't ruled out that a common factor like genetics could be causing both the emotions and the high blood pressure." Explain what this sentence means.
researchers may be concerned w confounding that occurs when effects of 2 or more explanatory variables are not separated or when there are some explanatory variables that were not considered in study but that affect value of response variable
Researchers wanted to determine if there was an association between daily coffee consumption and the occurence of heart disease. The researchers looked at 93, 933 women and asked them to report their coffee-drinking habits. The researchers also determined which of the women had congestive heart failure. After their analysis, the researchers concluded that consumption of 6 or more cups of caffeinated coffee per day was associated with a reduction in congestive heart failure. In their report, the researchers stated that "after adjusting for various demographic and lifestyle variables, daily consumption of 6 or more cups was associated with a 30% reduced prevalence of congestive heart failure." Why was it important to adjust for these variables?
researchers may be concerned w confounding that occurs when effects of 2 or more explantory variables are not separated or when there are some explanatory variables that were not considered in study but that affect value of response variable
A closed question requires
respondent to choose from list of predetermined responses
open question allows
respondent to choose his or her response.
Discuss a possible advantage of offering rewards or incentives to increase response rates.
respondents put more effort into completely and accurately answering survey questions because feel obligated.
An anti-smoking advocate wants to estimate the percentage of people who favor decreasing the use of advertising to sell cigarettes. She conducts a nationwide survey of 1070 randomly selected adults 18 years and older. The interviewer asks the respondents "Do you favor higher health insurance premiums for smokers?" Which of these best describes the bias in the survey?
response bias
Suppose you are conducting a survey regarding empathy among children in a school district. You obtain a cluster sample of 19 schools within a school district and sample all sophomore students in the randomly selected schools. The survey is administered by the parents. Which of these best describes the bias in the survey?
response bias
Researchers wanted to determine if having a supply of sugary snacks in the bedroom is associated with obesity. The researchers administered a questionnaire to 386 twelve year old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a supply of sugary snacks in their bedroom was significantly higher than that of the adolescents who did not have a supply of sugary snacks in their bedroom. What is the response variable in the study? Is the response variable qualitative or quantitative?
response variable is body mass index of the adolescents; quantitative
Researchers wanted to determine if there was an association between the level of satisfaction of an individual and their risk of high blood pressure. The researchers studied 1519 people over the course of 12 years. During this 12 year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of high blood pressure over the 12 year period. After their analysis, the researchers concluded that the satisfied individuals were less likely to experience high blood pressure. What is the response variable and why?
response variable is whether or not high blood pressure was contracted bc it is variable of interest
Researchers wanted to determine if there was an association between daily coffee consumption and the occurence of heart disease. The researchers looked at 93, 933 women and asked them to report their coffee-drinking habits. The researchers also determined which of the women had congestive heart failure. After their analysis, the researchers concluded that consumption of 6 or more cups of caffeinated coffee per day was associated with a reduction in congestive heart failure. What is the response variable in this study? Is the response variable qualitative or quantitative?
response variable is whether woman has congestive heart failure or not. response variable is qualitative
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. What conclusion was drawn from the study?
season of birth plays a role in one's temperament
A stratified sample is obtained by
separating population into nonoverlapping groups called strata & then obtaining simple random sample from each stratum.
Sony wants to administer a satisfaction survey to its current customers. Using their customer database, the company randomly selects 90 customers and asks them about their level of satisfaction with the company. What type of sampling is used?
simple random
Table: Setup: ABCDE Size (in): 58, 59, 56, 42, 43 Screen type: Projection, projection, plasma, plasma, plasma Number of type channels available: 299, 113, 425, 269, 289 What are the variables and their corresponding data?
size [58, 59, 56, 42, 43] screen type [projection, projection, plasma, plasma, plasma] and number of channels available [299, 113, 425, 269, 289]
Determined whether the underlined numerical value is a parameter or a statistic. Explain. In a national survey of high school students (grades 9 to 12), 25% of the students who responded reported that someone had offered, sold or given them an illegal drug on school property
statistic bc respondents who were high school students [grades 9 to 12] are a sample
To determine her air quality, Carrie divides up her day into three parts: morning, afternoon and evening. She then measures her air quality at 3 randomly selected times during each part of the day. What type of sampling is used?
stratified
Single-blind experiment
subject does not know which treatment is received
Sample
subset of population being studied
Suppose you are conducting a survey regarding empathy among children in a school district. You obtain a cluster sample of 19 schools within a school district and sample all sophomore students in the randomly selected schools. The survey is administered by the parents. How can the bias be remedied?
survey should be administered by impartial party
To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at IBM selects every 14th computer that comes off the assembly line starting with the seventh until she obtains a sample of 120 computers. What type of sampling is used?
systematic
Which sampling method does not require a frame?
systematic
A polling organization contacts 2658 teenagers who are 13 to 17 years of age and live in the United States and asks whether or not they had attended a concert this past year
teenagers who are 13 to 17 years of age and live in the united states
A polling organization contacts 2658 teenagers who are 13 to 17 years of age and live in the united states and asks whether or not they had attended a concert this past year What is the sample in this study?
the 2658 teenagers who are 13 to 17 years of age and live in the united states
Researchers studied 300 people and matched their personality type to when in the year they were born. They discovered that the number of people with a "cyclothymic" temperament, characterized by rapid, frequent swings between sad and cheerful moods, was significantly higher in those born in the autumn. The study also found that those born in winter were less likely to be excessively positive, while those born in spring were less likely to be depressive. What is the sample?
the 300 people in the study
A study conducted by researchers was designed "to determine if application of duct tape is as effective as cryotherapy in the treatment of common warts." The researchers randomly divided 60 patients into 2 groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were complete, it was determined that 73% of the patients in group 1 and 90% of the patients in group 2 had complete resolution of their warts. The researchers concluded that cryotherapy is significantly more effective in treating warts than duct tape. what is the sample?
the 60 patients w warts
Researchers wanted to test the effectiveness of a new drug therapy for treating patients with colon cancer. to do this, they identified 90 patients with a diagnosis of colon cancer. Patients were randomly assigned to one of three treatment groups. 30 patients were randomly assigned to receive the new drug therapy, another 30 received the older drug therapy and the final 30 received a placebo therapy. To measure the effectiveness of the treatment, researchers scored each patient on a standardized rating scale for colon cancer. After collecting and comparing the scores for the 3 treatment groups, the researchers concluded that the new drug therapy is significantly more effective than both the older drug therapy and the placebo therapy in the treatment of colon cancer. Identify the experimental units
the 90 patients w diagnosis of colon cancer
A phlebotomist draws the blood of a random sample of 50 patients and determines their blood types as shown. Contact a local hospital and ask them the percentage of the population that is blood type O. Why might the results differ
there is always variability bc individuals in survey may not exactly reflect makeup of population.
If variables did not vary,
they would be constants & statistical inference would not be necessary
An observational study measures
value of response variable without attempting to influence value of either response or explanatory variables
A variable is at the nominal level of measurement if
values of variable name, label or categorize naming scheme does not allow for values of variable to be arranged in ranked or specific order
A study conducted by researchers was designed "to determine if application of duct tape is as effective as cryotherapy in the treatment of common warts." The researchers randomly divided 60 patients into 2 groups. The 30 patients in group 1 had their warts treated by applying duct tape. The 30 patients in group 2 had their warts treated by cryotherapy. Once the treatments were complete, it was determined that 73% of the patients in group 1 and 90% of the patients in group 2 had complete resolution of their warts. The researchers concluded that cryotherapy is significantly more effective in treating warts than duct tape. What is the research objective?
to determine if duct tape is as effective as cryotherapy in treatment of warts
A gambler wanted to compare 2 types of poker strategies. One type is playing tight and the other is a loose style of play. It is a common belief that playing tight will win more pots. This belief is tested by having 10 poker players use each type of strategy in a game and comparing the number of pots won under each method of play. A coin flip was used to determine which type of poker strategy each player would follow first. Results indicated that there was no difference in the 2 types of strategy. Why is a coin used to decide the poker strategy each player would follow first?
to eliminate bias as to which strategy used first
true or false Randomization is used so that those factors not controlled in the experiment "average out" their effect on the response variable.
true
true or false Generally, the goal of an experiment is to determine the effect that the treatment will have on the response variable.
true
True or false. When conducting a cluster sample, it is better to have fewer clusters with more individuals when the clusters are heterogeneous
true bc when clusters are heterogeneous, they are scaled down versions of population
In addition, lurking variables are
typically related to explanatory variables in study.
Nonsampling error is the error that results from
undercoverage, nonresponse bias, response bias or data-entry errors
inferential statements
use known info to make predictions about unknown things that are related
For a poll of voters regarding a referendum calling for a national value-added tax, design a sampling method to obtain the individuals in the sample. Which sampling method would most likely be used in a poll of voters regarding a referendum calling for a national value-added tax?
use stratified random sampling since this is national issue, diff geographical locations are likely to have similar views
A retail manager wants to conduct a study regarding the shopping habits of his customers. He selects the first 60 customers who enter his store on a Saturday morning. What is a possible remedy?
use systematic random sampling
Inferential statistics
uses methods that generalize results obtained from sample to population & measure reliability of results
Determine whether the underlined value is a parameter or a statistic One of the greatest baseball hitters of all time has a career batting average of 0.366
value is parameter bc career at-bats of baseball player are a population
Describe whether the underlined value is a parameter or a statistic In a championship football game, a quarterback completed 59% of his passes for a total of 265 yards and 2 touchdowns
value is paramter bc quarterback's passes are a population
At end of cohort study,
value of respones variable is recorded for individuals
