Stats Exam Chapter 1
Which of the following is a reasonable way to reduce bias from nonresponse?
Offer incentives and use callbacks
What purpose does randomization serve in an experiment?
Randomization insures that the effect of factors whose levels cannot be controlled is minimized.
State whether the data described below are discrete or continuous, and explain why. The exact heights of students in a class.
The data are continuous because the data can take on any value in an interval.
State whether the data described below are discrete or continuous, and explain why. The numbers of majors offered by colleges.
The data are discrete because the data can only take on specific values.
Determine whether the data described below are qualitative or quantitative and explain why. The types of food served by restaurants (Italian, Chinese, fast, etc.)
The data are qualitative because they don't measure or count anything.
Determine whether the given value is a statistic or a parameter. A homeowner measured the voltage supplied to his home on 347 days of a given year, and the average (mean) value is 125.5 volts.
The given value is a statistic for the year because the data collected represent a sample. -347 is a sample of 365 days.
A company was conducting a survey to investigate people's spending habits and how they may have changed in recent years. One question on the survey was, "Did you spend more/less/the same amount of money this year as you did in 2007, the year the recession began in earnest in this country?" Is this question biased? If so, what answer does it favor?
This question is biased toward "spend less," since it mentions the recent recession. Many people would feel that they should answer that they spent less, since the country is in a recession.
A study of an association between which ear is used for cell phone calls and whether the subject is left-handed or right-handed began with a survey e-mailed to 5000 people belonging to an otology online group, and 717 surveys were returned. (Otology relates to the ear and hearing.) What percentage of the 5000 surveys were returned? Does that response rate appear to be low? In general, what is a problem with a very low response rate?
14% and appears to be low It creates a serious potential for getting a biased sample that consists of those with a special interest in the topic.
Suppose every student in a class is surveyed and it is reported that 75% of the class plans to take another math class. Is this an example of descriptive or interferential statistics? explain
Descriptive statistics; the results of the class sample are described without many any generalizations about the population of all students at the school (descriptive statistics describes data while interferential statistics makes generalizations about the population)
Determine if the following statement is true or false. A sample of 100 people was selected from a town of 10,000 residents. To get the same level of precision for a town of 50,000 residents, a sample of 500 would be needed.
False, because only the sample size matters, not the fraction of the overall population, the same sample size could be used for both populations.
An ad for a device used to discourage bike thefts stated that "This device reduces you odds of bike theft by 350%". What is wrong with this statement?
If the device eliminated all bike thefts, it would reduce the odds of bike theft by 100%, so the 350% figure is misleading. -This information can be misleading to consumers because 350% is not possible.
A polling company reported that 57% of 1013 surveyed adults said that cellular phones are cellular phones are "very harmful.""very harmful." Complete parts (a) through (d) below. a. What is the exact value that is 57% of 1013? b. Could the result from part (a) be the actual number of adults who said that cellular phones are "very harmful"? Why or why not? c. What could be the actual number of adults who said that cellular phones are "very harmful"? The actual number of adults with this opinion could be ________. d. Among the 1013 respondents, 348 said that cellular phones are "not at all harmful. What percentage of respondents said that cellular phones are "not at all harmful"?
a. 577.41 b. No, the result from part (a) could not be the actual number of adults who said that cellular phones are "very harmful" because a count of people must result in a whole number. c. 577 d. 34.35%
A medical study was investigating if getting a flu shot actually reduced the risk of developing the flu. From a group of adult volunteers, researchers randomly assigned half to receive an injection that contained the drug believed to reduce the risk of getting the flu and the other half to receive an injection containing no active ingredient (i.e. sugar water). Because the control group received a placebo, what type of study was performed?
blinded
which of the following would not cast doubt of the usefulness of sample data? a. nonresponse b. missing data c. an effective sampling method d. order of questions in a survey
c. an effective sampling method -all of the other choices can make a sample data not accurate
Which of the following is not a misuse of statistics? a. making conclusions about a population based on a voluntary response sample b. misleading graphs c. utilizing valid statistical methods and correct sampling techniques d. concluding that a variable causes another variable because they have some correlation
c. utilizing valid statistical methods and correct sampling techniques -this option is a correct method of using stats while the other choices are a misuse
Identify which type of sampling is used: random, systematic, convenience, stratified, or cluster. To determine customer opinion of their safety features, Daimler−Chrysler randomly selects 100 service centers during a certain week and surveys all customers visiting the service centers.
cluster -population area was divided into sections (different service centers), sections were randomly picked, all members from the selected clusters are chosen
Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below. A man is selected by a marketing company to participate in a paid focus group. The company says that the man was selected because everyone in four randomly selected towns was being selected.
cluster sampling -population area was divided into sections, sections were randomly picked, all members from the selected clusters are chosen
Identify which of these designs is most appropriate for the given experiment: completely randomized design, randomized block design, or matched pairs design. Currently, there is no approved vaccine for the prevention of infection by a certain virus. A clinical trial of a possible vaccine is being planned to include subjects treated with the vaccine while other subjects are given a placebo. The most appropriate is ________________ design.
completely randomized -uses randomness to assign placebos
Elmo likes music. He wondered if listening to music while studying will improve scores on an exam. Fifty students who were to take the midterm in a week agreed to be part of a study. Half were randomly assigned to listen to classical music while studying for the exam. The other half were told not to listen to any music while studying for the exam. What type of study is being performed?
completely randomized experimental design
which of the following is not a voluntary response sample? a. a local dentist asks her patients to fill out a questionnaire and mail it back to determine the quality of care b. radio station asks for call-in responses c. survey at mall asking passerbys to fill out surveys d. quiz scores from a college level stats course determine student progress
d. quiz scores from a college level stats course determine student progress -all of the other options are voluntarily filled out
In a television advertisement, a company called "Waist Away" claimed the workout program on their set of DVDs would help people lose weight more than any other DVD workout program. To test this claim, an independent company, called "Slim Down," selected one other DVD program. They then randomly assigned half the volunteers to the Waist Away program and the other half to the Slim Down program. Each participant was weighed before they started the program and then regularly participated in their assigned program for one month. After one month, each participant was weighed again. The percent of weight lost was recorded for each person, where negative values indicated a weight gain. What type of study was performed?
experiment -treatment was applied and tested
A quantitative variable can be at which levels of measurement?
interval or ratio -have numerical significance meaning it cannot be below the interval level
A qualitative variable can be at which levels of measurement?
nominal or ordinal -qualitative variables are not numerical (or do not have numerical significance) so they cannot go above the ordinal level
Do people walk faster in an airport when they are departing (getting on a plane) or after they have arrived (getting off a plane)? An interested passenger watched a random sample of people departing and a random sample of people arriving and measured the walking speed (in feet per minute) of each. What type of study design is being performed?
observational study -subjects are not modified, just observed
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate. Birth order among siblings in a family.
ordinal -can be order but no differences
A __________ is a numerical measurement describing some characteristic of a population.
parameter; characteristic of a population not a sample
The ____________ is/are the entire group of individuals or items being studied.
population; is a complete collection of all measurement/data
Identify the type of observational study (cross-sectional, retrospective, or prospective) described below. A research company uses a device to record the viewing habits of about 7500 households, and the data collected over the next 5 years will be used to determine whether the proportion of households tuned to a particular children's program decreases.
prospective study -data is collected in the future
Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below. In a poll conducted by a certain research center, 732 adults were called after their telephone numbers were randomly generated by a computer, and 80% were able to correctly identify the vice president.
random sampling -randomly picked to avoid bias
When the survey design influences the responses, by asking leading questions for example, it is called ______________. When a large fraction of those sampled fail to respond to a survey, it is called _____________.
response bias nonresponse bias
The _________ is/are a subject of the population that is being studied.
sample; sub collection of members from a population
A __________ is a numerical measurement describing some characteristic of a sample.
statistic; characteristic of a sample, not population
Identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster. To determine her mood, Carrie divides up her day into three parts: morning, afternoon, and evening. She then measures her mood at 4 randomly selected times during each part of the day.
stratified -the day is subdivided into 3 subgroups and mood sample is collected from each subgroup
Identify the type of sampling used: random, systematic, convenience, stratified, or cluster. To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Toyota selects every 18th car that comes off the assembly line starting with the eighth until she obtains a sample of 80 cars.
systematic -every 18th car is selected
A telephone survey is conducted for a public-opinion poll using a frame that consists of all households in the city with a telephone. Since this sampling method excludes any households without a telephone number and homeless individuals, what type of bias is present?
undercoverage
A newspaper posted this question on its website: "How often do you seek medical information online?" Of 1072 Internet users who chose to respond, 38% of them responded with "frequently." What term is used to describe this type of survey in which the people surveyed consist of those who decided to respond? What is wrong with this type of sampling method? What term is used to describe this type of survey? Select all that apply. A. The respondents are a self-selected sample. B. The respondents are a census. C. The respondents are a population. D. The respondents are a voluntary response sample. What is wrong with this type of sampling method? Select all that apply. A. It is too expensive. B. The survey question is "loaded," or intentionally worded to elicit a desired response. C. Many people may choose not to respond to the survey. D. It is too time consuming. E. Responses may not reflect the opinions of the general population.
A. The respondents are a self-selected sample. AND D. The respondents are a voluntary response sample. C. Many people may choose not to respond to the survey. AND E. Responses may not reflect the opinions of the general population. -The respondents chose to take the survey making it both a self-selected sample and voluntary response sample. -Because the survey is optional, many people would choose not to do it. Since only a small percentage chose to take it, it cannot accurate describe the opinions of the general population.
Explain why Social Security Number is considered a qualitative variable even though it contains numbers.
Addition and subtraction of Social Security Numbers does not provide meaningful results. This makes it qualitative even though it is numeric.
A researcher was once criticized for falsifying data. Among his data were figures obtained from 6 groups of mice, with 20 individual mice in each group. These values were given for the percentage of successes in each group: 53%, 58%, 63%, 46%, 48%, 67%. What's wrong with those values?
All percentages of success should be multiples of 5.. The given percentages cannot be correct. -There are 20 individual mice. 100 divided by 20 is 5.
Explain why city altitude is a variable at the interval and not ratio level of measurement.
Differences in altitudes can be found and are meaningful. However, there is no natural zero starting point since sea level varies over geological time scales.
What must be true for a sample to be considered a simple random sample?
Every member (or sample) must have the same chance of being selected as every other member (or sample of the same size).
Suppose every student in a class is surveyed and it is found that 75% o the class plans to take another math class. it is reported that 75% of all students at the school plan to take another math class. Is this an example of descriptive of interferential statistics? Explain.
Inferential statistics; the results of the class sample are extended to make a generalization about the population of all students at the school. (inferential stats make a generalization about a population)
In the data table below, the x-values are the weights (in pounds) of cars and the y-values are the corresponding highway fuel consumption amounts (in mi/gal). Given the context of the car measurement data, what issue can be addressed by conducting a statistical analysis of the values?
Is there a relationship or an association between the weight of a car and its fuel consumption amount?
Determine whether the sampling method described below appears to be sound or is flawed. In a survey of 556 human resource professionals, each was asked about the importance of the education of a job applicant. The survey subjects were randomly selected by pollsters from a reputable market research firm.
It appears to be sound because the data are not biased in any way. -There is not bias because it is a population of human resource professionals.
Determine whether the sampling method described below appears to be sound or is flawed. In a survey of 798 subjects, each was asked how often he or she drank milk.drank milk. The survey subjects were internet users who responded to a question that was posted on a news website.
It is flawed because it is a voluntary response sample. -The subjects were given the choice to do the survey, making the results not representative of the whole population.
What purpose does replication serve in an experiment?
Replication insures that the effect of a treatment is not due to some characteristic of a single experimental unit.
In a study designed to test the effectiveness of a medication as a treatment for lower back pain, 1643 patients were randomly assigned to one of three groups: (1) the 547 subjects in the placebo group were given pills containing no medication; (2) 550 subjects were in a group given pills with the medication taken at regular intervals; (3) 546 subjects were in a group given pills with the medication to be taken when needed for pain relief. In what specific way was replication applied in the study?
The group sample sizes are all large so the researchers could see the effects of the treatment.
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate for the data below. Years in which an Olympics was held
The interval level of measurement is most appropriate because the data can be ordered, differences (obtained by subtraction) can be found and are meaningful, and there is no natural starting zero point. -differences are meaningful, but no natural zero starting point and ratios are meaningless
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate for the data below. Internet speed levels of "fast comma " "medium comma " and "slow"
The ordinal level of measurement is most appropriate because the data can be ordered ,but differences( obtained by subtraction) cannot be found or are meaningless.
An article noted that chocolate is rich in flavonoids. The article reports that "regular consumption of foods rich in flavonoids may reduce the risk of coronary heart disease." The study received funding from a candy company and a chocolate manufacturers association. Identify and explain at least one source of bias in the study described. Then suggest how the bias might have been avoided.
The researchers may have been more inclined to provide favorable results because funding was provided by a party with a definite interest. The bias could have been avoided if the researchers were not paid by the candy company and the chocolate manufacturers. -Because this study was funded by a candy company, it is very likely this study was biased.
A particular country has 40 total states. If the areas of 20 states are added and the sum is divided by 20, the result is 199,312 square kilometers. Determine whether this result is a statistic or a parameter.
The result is a statistic because it describes some characteristic of a sample. -it uses only 20 states instead of 40.
A healthcare company is interested in knowing how many pediatricians in a large metro area are available to their patients through email or other online communication. The healthcare company takes a systematic sample of 40 doctors from the phone book and calls the selected offices to determine the information. Is this sampling plan appropriate? Why or why not?
The sampling plan is not appropriate, since it will result in undercoverage of doctors who are not listed in the phone book.
Determine whether the source given below has the potential to create a bias in a statistical study. A certain medical organization tends to oppose the use of meat and dairy products in our diets, and that organization has received hundreds of thousands of dollars in funding from an animal rights foundation.
There does appear to be a potential to create a bias. There is an incentive to produce results that are in line with the organization's creed and that of its funders. -The organization is being funded by an organization that would support to the opposition of meat and dairy products in our diets. They may lose the funding if they go against that organization.
Determine whether the study is an experiment or an observational study, and then identify a major problem with the study. In a survey, 1465 Internet users chose to respond to this question posted on a newspaper's electronic edition: "Is news online as satisfying as print and TV news?" 52% of the respondents said "yes." What is a major problem with the study?
This is an observational study because the researchers do not attempt to modify the individuals. This is a convenience sample with voluntary response, which has a high chance of leading to bias.
In a study of a weight loss program, 4 subjects lost an average of 40 lbs. It is found that there is about a 37% chance of getting such results with a diet that has no effect. Does the weight loss program have statistical significance? Does the weight loss program have practical significance?
No, the program is not statistically significant because the results are likely to occur by chance. -The percentage is not high enough to show the weight loss program is the reason they lost weight because they could have lost this amount of weight without the program by chance. Yes, the program is practically significant because the amount of lost weight is large enough to be considered practically significant. -Since these subject lost a large amount of weight, it is practical.
