STAT 101 Chapters 9-12 Quiz
Which of the following is NOT a random event?
Deciding which direction you will go when you approach a stop sign.
Trial
Each occasion upon which a random phenomenon is observed is called a(n)
cluster sample
is used when it is difficult to get a sampling frame for a large population. The sample is selected by dividing the population into clusters and randomly selecting a certain number of clusters.
stratified random sample
is used when large populations are made up of smaller homogenous (similar) groups. The sample consists of a simple random sample from each group.
Parameters are numerical summaries about the ___________ and are usually ______________ to know with certainty.
population impossible
Theoretical
probability is based a mathematical model with assumptions.
Empirical
probability is based on the long term behavior of an event.
Which of the following denote statistics
r p-hat y-bar s
Statistics are numerical summaries about the ____________ and are ____________ to calculate.
sample possible
What is the minimum number of levels that a factor can have?
2
response bias
Leading questions and the possibility that people will not answer truthfully can result in
census
is a survey of the entire population.
An observational study...
CAN show association between variables, but CANNOT show causation
Flipping a coin with both sides heads is a random event.
False
levels
The specific values the experimenter choose for a factor are called
Which of the following denote parameters
rho mu sigma p
Sample-to-sample differences in statistics are referred to as ____________.
sampling variability
Random numbers are a list of numbers 0 through 9 ______________.
that have equal chance of being chosen
event
A combination of possible outcomes is called a(n
placebo
A fake treatment that resembles a real treatment is referred to as a
Which of the following is NOT a random event?
A person picking a number between 1 and 10.
Instead, as you are about to randomly draw a chip from the bag, you bet your friend you will pick a blue chip because you have already drawn and replaced a chip from the bag 10 times and picked 6 blue chips, 1 red chip, and 3 white chips. What type of probability did you use to justify your bet of drawing a blue chip out of the bag?
Empirical Probability
The disadvantages of taking a census are:
I. It can be very difficult to complete a census. III. Populations usually change constantly. IV. It can be more complex and time consuming than regular sampling.
Which sampling methods, if used correctly, produce a sample that is representative of the population?
I. Simple Random Sample III. Stratified Random Sample IV. Multistage Sample
How popular is Twitter with undergraduate students at your college or university? One proposal for sampling students to estimate the proportion of undergraduates who have a Twitter account is to ask the Registrar's office to give you a list of 200 randomly selected students with email and mailing addresses and phone numbers. All undergraduates are included in the list the Registrar uses to select the random sample of 200 students. You believe all students surveyed will answer the question truthfully. Your sample survey could still be subject to what type of bias?
Non-response bias
psos Public Affairs plans to conduct a public opinion survey in the states of Iowa and Texas. In each state, 1,000 randomly selected adults will be contacted and asked the question, "Generally speaking, would you say that things in this country are heading in the right direction?" Which sample will provide more information about the respective state's population - the sample from Iowa or the sample from Texas?
Neither - both samples will provide the same information about their prospective populations
simulation
Repeating an event multiple times is called a
Select the four principles of experiments.
Replication Blocking Randomization Control
Suppose that you have a hat filled with 10 white chips, 10 red chips, and 10 blue chips, all the same size. You mix the chips up with your hand, then without looking, you select a chip from the hat. Select the correct statement below.
Selecting the chip from the hat is a random event since you do not know the color of the chip before you select it from the hat.
Assume you have a poker chip set containing blue, red, and white chips, all of the same size. You place 15 blue chips, 10 red chips, and 25 white chips in a bag. As you are about to randomly draw a chip from the bag, you bet your friend you will pick a red chip from the bag because you feel that red is your lucky color. What type of probability did you use to justify your bet of drawing a red chip out of the bag?
Subjective/Personal Probability
Probability
The chance of an event occurring is called the event's
sample space
The collection of all possible outcomes is called the
treatments
The combination of factors and levels in the experiment is called the
Control group
The group that receives no treatment is referred to as a
response variable
The outcome of an experiment is called a
Replication
The process of assigning multiple experimental units to the same treatment.
Randomization
The process of assigning treatments to experimental units.
outcome
The value of the random phenomenon is called a(n
Instead, as you are about to randomly draw a chip from the bag, you bet your friend that you will pick a white chip from the bag because you know that there is a 0.5 probability that the chip you select will be white (as opposed to 0.3 for blue and 0.2 for red). What type of probability did you use to justify your bet of drawing a white chip out of the bag?
Theoretical Probability
A representative sample is one that accurately characterizes the entire population.
True
A survey was conducted to determine support for President Obama in the 2012 election in the state of Iowa. The survey collected data from a random sample from each of Iowa's four current congressional districts. This will produce a sample that is representative of the population.
True
How popular is Twitter with undergraduate students at your college or university? One proposal for sampling students to estimate the proportion of undergraduate who have a Twitter account is to randomly select a dorm on campus and ask every person who lives in the dorm if they have a Twitter account. Suppose you were able to interview everyone living in this dorm and you believe all students surveyed answered the question truthfully. Your sample survey will still be subject to what type of bias?
Undercoverage
Blocking is used to remove identifiable sources of ________.
Variation
confounding
When levels of one factor are associated with levels of another factor, this is called
Convenience sample
When participants are chosen for a sample based on ease of access it is called a
A sampling frame is
a list of every case in the population
How popular is Twitter with undergraduate students at your college or university? One proposal to estimate the proportion of all undergraduates who have a Twitter account is to take a sample of 200 students from the directory and contact them by phone, email, and letter and ask them if they have a Twitter account. Select the best description of the sampling frame.
all undergraduates at the college or university who are listed in the directory
The bean pod mottle virus (BPMV) is a virus found in soybeans spread by the bean leaf beetle. Concerned with the health of his own field of soybeans, a soybean farmer decided to conduct a small study to compare pesticides. He had 5 acres of land, far from any trees to prevent any area getting less sunlight, that he separated into 30 plots and planted 40 soybean plants per plot. He then randomly chose 10 plots to receive his usual pesticide, 10 plots to receive a new organic pesticide, and the last 10 plots were left untreated (given no pesticide). Also, to maintain constant conditions across the field, each plot was watered equally by the same farmer and using the same equipment. Once the soybean season was over, the farmer recorded the proportion of infected soybean plants from the 40 plants in each of the 30 plots. Match the following experimental principles with how they are represented in this experiment. -control -randomization -replication
control: Every plot received equal sunlight and water. randomization: The farmer randomly chose which plots would receive which treatment. Replication: There are 10 plots in each treatment group.
The Law of Large Numbers states that as you repeat more trials of a random event, the __________probability of an event gets closer to the _______________ probability of the event.
empirical theoretical
Simple Random Sample
every combination of population members has an equal chance of being selected for the sample.
The variable being manipulated by the researcher in order to observe a response is called a _______.
factor
multistage sample
is a combination of simple random, stratified and cluster sampling.
The bean pod mottle virus (BPMV) is a virus found in soybeans spread by the bean leaf beetle. Concerned with the health of his own field of soybeans, a soybean farmer decided to conduct a small study to compare pesticides. He selected 5 acres of land, far from any trees to prevent any area getting less sunlight, that he separated into 30 plots and planted 40 soybean plants per plot. He then randomly chose 10 plots to receive his usual pesticide, 10 plots to receive a new organic pesticide, and the last 10 plots were left untreated (given no pesticide). Also, to maintain constant conditions across the field, each plot was watered equally by the same farmer and using the same equipment. Once the soybean season was over, the farmer recorded the proportion of infected soybean plants from the 40 plants in each of the 30 plots. In this experiment, what type(s) of randomization was implemented?
random assignment only
Does regular exercise lead to higher VO2 Max? VO2 Max is the maximum amount of oxygen, in milliliters, one can use in one minute per kilogram of body mass. A random sample of 20 college age women was selected. Each student was asked whether or not they exercised regularly (at least 30 minutes of aerobic exercise 3 times a week) during the last year. The VO2 Max for each student was also taken and the relationship between their past exercise habits and current V02 Max was studied. What type of study was conducted?
retrospective study
he outcome of a random event is ______________.
unknown before the event occurs and the long term behavior of the event is known
When first introduced, the Xbox video game system had some serious flaws. Numerous systems were over heating which would cause the game to crash after playing for a while. In order to correct the problem, experts suggested either adding an extra fan to disperse heat or installing one higher quality fan. To decide the best approach, a group of engineers at Microsoft conducted a study. Thirty Xbox machines were randomly selected from the assembly line, right before the usual fan was installed. Once selected, the engineers rolled a dice to decide which fan or fans to install in the machine. If they rolled 1 or 4, the machine received the old fan. If they rolled 2 or 5, the machine received two old fans. Finally, if they rolled a 3 or 6, the machine received the higher quality fan. This was done so that there were ten machines in each of the treatment groups. Once the Xbox machines were completely assembled, they were then taken to a large room keep at a constant 72 degrees Fahrenheit with 30 different stations setup in equally spaced distances across the room. Each station had the same style television and television stand. Once in their stations, all of the Xbox machines were run with the same graphic intensive game for as long as it took for the machine to overheat. The time until each machine overheats was recorded in minutes. How much replication was used in this experiment?
10 machines in each treatment group
n February 16, 1998 edition of the Des Moines Register, randomly selected Iowans aged 18 or older were asked "Do you favor a proposal to prohibit 16-year-olds from driving between midnight and 6 am unless accompanied by an adult?" Which sample size would give the Des Moines Register the most information about the opinion of the population?
1200
A person with O+ blood type can only receive blood from donors with O blood type. Around 44% of the population has O blood type. Using 00 through 43 to indicate a person with O blood type and 44 through 99 to indicate a person with another blood type, use the random numbers below to determine how many people out of 10 donors showing up at a blood fair have type O blood. 22329 75886 08457 51276
4
What are the 3 main ideas of sampling?
I. Selecting a sample of the population. II. Selecting the sample randomly from the population. V. Obtaining a larger sample from a large population and a smaller sample from a small population.
undercoverage
If some portion of the population is excluded from the sampling frame, this is called
The population is
-Larger than the sample. -The entire group of cases we want information on. -Impractical or too expensive to collect information from.
Concerned about reports of discolored scales on fish caught downstream from a new chemical plant, scientists set up a field station in a shoreline public park. For one week, they asked fishermen there to bring any fish caught to the field station for a brief inspection. At the end of the week, the scientists found that 18% of the 234 fish submitted for inspection displayed the discoloration. Population Sample Population Parameter Sample Statistic
-Population: All (legally) catchable fish living downstream from the chemical plant during this week. -Sample: The 234 fish that were caught and brought to the field station. -Population Parameter: percent of all (legally) catachable fish living downstream from the chemical plant that had discolored scales. -Sample Statistic: 18%
The Sample is
-Smaller than the population -Typically used instead of the population to gather information from
The local county Board of Supervisors is thinking about enacting an ordinance that would require the registration of beer kegs sold in the county. The Board of Supervisors wants to get input from students at the local university on the proposed ordinance. Listed below are some ideas proposed for gathering data on students' opinions of the ordinance. Match the ideas on the left to the corresponding sampling strategy on the right. -Voluntary response sample: -Convenience sample: -Cluster sample -simple random sample -systematic sample
-Voluntary response sample: Put an ad in the local paper asking students to log their opinions on the Board of Suprevisors web site. -Convenience sample: Visit the local liquor store and ask students coming in to buy beer their opinions. -Cluster sample: Select a dorm on campus at random and contact every resident in the dorm to get his/her opinion. -simple random sample: Randomly select 100 students from the directory and contact them by phone to get their opinions. -systematic sample: Ask the Registrar to select every 250th students, starting with the 111th student, on the list of all students enrolled at at the university and provide addresses, phone numbers and emails so that those students selected can be contacted to get their opinions.
How popular is Twitter with undergraduate students at your college or university? Listed below are some ideas for sampling students to estimate the proportion of all undergraduate students who have a Twitter account. Match the proposal on the left to the sampling strategy employed on the right. -convenience sample: -voluntary response sample -cluster sample -stratified sample -simple random sample
-convenience sample: Interview your friends -voluntary response sample: Put an ad in the campus newspaper asking students to log into a survey on their website. -cluster sample: Randomly select a dorm campus and contact every resident in the dorm. -stratified sample: Ask the Registrar's office on campus to randomly select 50 Freshmen, 50 Sophomores, 50 Juniors and 50 Seniors for your sample and to provide you with phone numbers, email addresses and mailing addresses for each. -simple random sample: Ask the Registrar's office on campus to randomly select 200 undergraduate students for your sample and to provide you with email addresses, phone numbers, and mailing addresses for each student selected.
The following is taken from an article in the Des Moines Register, January 14, 2007, page 4AA titled "Milk blunts heart benefits of tea:" There are a lot of studies that show that tea is protective against cardiac diseases, said lead researcher Dr. Verena Stangl, professor of cardiology at the Charite Hospital, Universitatsmedizin-Berlin, in Germany. If you look at the studies, you see that in Asia there are less cardiac diseases, but in England that's not the case. So the question is, is the addition of milk a reason for this difference between Asia and England, where tea is often taken with milk? In the study, 16 healthy postmenopausal women drank either half a liter of freshly brewed black tea, black tea with 10 percent skimmed milk, or boiled water on three different occasions. The researchers then measured the function of the cells lining the brachial artery in the forearm before and two hours after beverage consumption. Stangl's team found that black tea significantly improved the ability of the arteries to relax and expand. But when they added milk, they found the biological effect of the tea was completely abolished. Match the term on the left to the correct description on the right. -experimental units -response variable -factor -treatments
-experimental units: 16 healthy postmenopausal women -response variable: How much the brachial artery relax and expand. -factor: The beverage the participants drink. -treatments: Black tea, black tea with milk or boiled water.
In a CNN/USA Today/Gallop poll of 1,200 randomly selected adults in the United States conducted between October 13 and October 16, 2005, 58% of those surveyed said they disapproved of the way George W. Bush is handling his job as president. Match the term on the left with the correct description on the right. -population -sample -population parameter -sample statistic
-population: Adults in the US -sample: 1,200 adults in the US -population parameter: percent of all adults in the United States who disapproved of the way George W. Bush is handling his job as president. -sample statistic: 58%
The following excerpt is taken from an article that appeared in the Des Moines Register on Saturday, March 4, 2000 titled "Meditation helps clear clogged arteries:" Trancendental meditation to reduce stress helped clear clogged arteries in a group of African-Americans, a study published Friday shows. The study used to ultrasound to measure the thickness of the carotid artery wall in 60 African-Americans. The researchers recruited 60 African-American men and women with high blood pressure in the Los Angeles area. One group was taught transcendental meditation and practiced it for 20 minutes twice a day. A second group received health education, then spent 20 minutes, twice a day, engaged in leisure activities such as reading or exercise. After seven months, the meditating group had a mean reduction in artery wall thickness of 0.098mm. The wall thickness in the control group increased by 0.054mm. Match the term on the left to the correct description on the right. -response variable -experimental units -factor -treatments
-response variable; The thickness of the carotid artery wall -experimental units: 60 African-American men and women with high blood pressure living in the LA area. -factor: The use of transcendental meditation. -treatments: Transcendental meditation and practicing it 20 minutes twice a day, receiving health education and spending 20 minutes twice a day engaged in leisure activities.
Around 10% of the male population have some color perception defect, most commonly red-green color blindness. Select the most appropriate method for assigning random numbers from the random number table to simulate this value.
0 is a male with color perception difficulties, 1 through 9 is a male without color perception difficulties.
Around 50% of the population are men. Select the most appropriate method for assigning random numbers from the random number table to simulate this value.
0 through 4 is a male, 5 through 9 is a female.
Assume you have a poker chip set containing blue, red, and white chips, all of the same size. You place 30 blue chips, 20 red chips, and 50 white chips in a bag. Using the Law of Large Numbers, what is the probability of selecting a blue chip from the bag? (Report the probability to 2 decimal places, eg. 0.14)
0.30
Assume you have a poker chip set containing blue, red, and white chips, all of the same size. This time, you place 18 blue chips, 23 red chips, and 9 white chips in a bag. Using the Law of Large Numbers, what is the probability of selecting a red chip from the bag? (Report the probability to 2 decimal places, eg. 0.14)
0.46
The American College of Obstetricians and Gynecologists says that out of every 100 babies born in the United States, 3 have some kind of major birth defect. Select the most appropriate method for assigning random numbers from a random number table to simulate this value.
00 through 02 denotes a baby born with a major birth defect, 03 through 99 denotes a baby born without a major birth defect.
A basketball player makes his free throw attempts 72% of the time. Select the most appropriate method for assigning random numbers from the random number table to simulate this statistic.
00 through 71 indicates a made free throw, 72 through 99 indicates a missed free throw.
Your friend is taking another class this semester that uses online homework assignments. Instead of studying, your friend decides to complete the 10 question assessment with all multiple choice questions randomly. The multiple choice questions all have 5 possible answers, so there is only a 20% chance of getting the correct answer if choosing randomly. Using a 0 through 1 to indicate a correct answer and a 2 through 9 to indicate an incorrect answer, use the random numbers below to determine how many of the 10 questions your friend correctly answered on this homework assignment.
1
Systematic sample
A sample selected by choosing every 10th person from a list of the populaton is called a
retrospective study
A study that looks at data that has already been collected is called a(n)
prospective study
A study that looks at data which will be collected in the future is called a(n)
A company made of 4 sectors has noticed that employee morale is down. The 4 sectors are: 450 packaging employees, 700 manufacturing employees, 75 distribution employees, and 12 managers. In an effort to understand the slump in morale, the company is planning on conducting interviews with a sample of employees from each group. Below are the last names of the 12 managers. Use the random numbers below to choose 2 people for the sample. 01 Barrett 02 Grigorov 03 Smithson 04 Bowman 05 Maceli 06 Tadros 07 Chen 08 Mulvaney 09 Thraen 10 DeLara 11 Pagliarulo 12 Williams Random Numbers: 21619 45301 93301 69272 43883 66925 15617 60790
Barrett and Chen
An experiment
CAN show causation between variables because the treatments are randomly assigned
How popular is Twitter with undergraduate students at your college or university? Assume you interview your friends and find out what proportion of them have a Twitter account. This will produce a sample that is representative of the population.
False
The following excerpt is taken from an article that appeared in the Des Moines Register on Saturday, March 4, 2000 titled "Meditation helps clear clogged arteries:" Trancendental meditation to reduce stress helped clear clogged arteries in a group of African-Americans, a study published Friday shows. The study used to ultrasound to measure the thickness of the carotid artery wall in 60 African-Americans. The researchers recruited 60 African-American men and women with high blood pressure in the Los Angeles area. One group was taught transcendental meditation and practiced it for 20 minutes twice a day. A second group received health education, then spent 20 minutes, twice a day, engaged in leisure activities such as reading or exercise. After seven months, the meditating group had a mean reduction in artery wall thickness of 0.098mm. The wall thickness in the control group increased by 0.054mm. This experiment used a placebo.
False
The following is taken from an article in the Des Moines Register, January 14, 2007, page 4AA entitled Kidney disease linked to blood flow problems: People with chronic kidney disease have an increased risk of peripheral arterial disease (PAD), a condition that causes reduced blood flow in the legs and can lead to amputation. In the study, more than 14,000 middle age adults were enrolled and followed for an average of 13 years. The participants were split into three groups: those with normal kidney function; those with mildly decreased kidney function; and those with late stage chronic kidney disease. After adjusting for age, race, and sex, the study authors found the rate of PAD was nearly two times higher in chronic kidney disease participants than in people with normal kidney function. This is an experiment.
False
Statistical Significance
The results of an experiment when the observed differences between treatment groups are much larger than the differences expected due to random assignment.
As a part of a research project, you would like to determine the proportion of undergraduates at your college or university who have committed academic dishonesty (cheated) at some point during their time as a student. To obtain a sample, you ask the Registrar's office to give you a list of 200 randomly selected students with email and mailing addresses and phone numbers. All undergraduates are included in the list the Registrar uses to select the random sample of 200 students and you receive all surveys back from the 200 students. Your sample survey could still be subject to what type of bias?
Response Bias
When first introduced, the Xbox video game system had some serious flaws. Numerous systems were over heating which would cause the game to crash after playing for a while. In order to correct the problem, experts suggested either adding an extra fan to disperse heat or installing one higher quality fan. To decide the best approach, a group of engineers at Microsoft conducted a study. Thirty Xbox machines were randomly selected from the assembly line, right before the usual fan was installed. Once selected, the engineers rolled a dice to decide which fan or fans to install in the machine. If they rolled 1 or 4, the machine received the old fan. If they rolled 2 or 5, the machine received two old fans. Finally, if they rolled a 3 or 6, the machine received the higher quality fan. This was done so that there were ten machines in each of the treatment groups. Once the Xbox machines were completely assembled, they were then taken to a large room keep at a constant 72 degrees Fahrenheit with 30 different stations setup in equally spaced distances across the room. Each station had the same style television and television stand. Once in their stations, all of the Xbox machines were run with the same graphic intensive game for as long as it took for the machine to overheat. The time until each machine overheats was recorded in minutes. What aspects of this study were NOT used in an attempt to control outside variables?
The 30 Xbox machines were randomly selected from the assembly line.
When first introduced, the Xbox video game system had some serious flaws. Numerous systems were over heating which would cause the game to crash after playing for a while. In order to correct the problem, experts suggested either adding an extra fan to disperse heat or installing one higher quality fan. To decide the best approach, a group of engineers at Microsoft conducted a study. Thirty Xbox machines were randomly selected from the assembly line, right before the usual fan was installed. Once selected, the engineers rolled a dice to decide which fan or fans to install in the machine. If they rolled 1 or 4, the machine received the old fan. If they rolled 2 or 5, the machine received two old fans. Finally, if they rolled a 3 or 6, the machine received the higher quality fan. This was done so that there were ten machines in each of the treatment groups. Once the Xbox machines were completely assembled, they were then taken to a large room keep at a constant 72 degrees Fahrenheit with 30 different stations setup in equally spaced distances across the room. Each station had the same style television and television stand. Once in their stations, all of the Xbox machines were run with the same graphic intensive game for as long as it took for the machine to overheat. The time until each machine overheats was recorded in minutes. Select the best description of how the treatments were randomly assigned to the experimental units.
The engineers rolled a dice to decide which fan or fans to install in the machine.
Rolling a die where the chance of a rolling a 1 through 5 is 15% each and the chance of rolling a 6 is 25% is a random event.
True
The following is taken from an article in the Des Moines Register, January 14, 2007, page 4AA titled "Milk blunts heart benefits of tea:" There are a lot of studies that show that tea is protective against cardiac diseases, said lead researcher Dr. Verena Stangl, professor of cardiology at the Charite Hospital, Universitatsmedizin-Berlin, in Germany. If you look at the studies, you see that in Asia there are less cardiac diseases, but in England that's not the case. So the question is, is the addition of milk a reason for this difference between Asia and England, where tea is often taken with milk? In the study, 16 healthy postmenopausal women drank either half a liter of freshly brewed black tea, black tea with 10 percent skimmed milk, or boiled water on three different occasions. The researchers then measured the function of the cells lining the brachial artery in the forearm before and two hours after beverage consumption. Stangl's team found that black tea significantly improved the ability of the arteries to relax and expand. But when they added milk, they found the biological effect of the tea was completely abolished. The control group in this experiment is __________.
The group who drank the boiled water.
Repeatability
The process of conducting the entire experiment again.
Blocking
The process of dividing experimental units into similar groups prior to the experiment.
Control
The process of keeping all other variables except the treatment the same for all experimental units.
Random assignment
The process used to randomize the treatments to the experiment units.
Random Selection
The process used to randomly select the experimental units.
Random Ordering
The process used when there is a sequential nature to the experiment.
An ultramarathon is a foot race that is longer than 26.2 miles. Doctors have found that people who run an ultramarathon are at increased risk for developing respiratory infections after the race. Doctors believe that taking vitamin C the 10 days before and the 10 days after the race would reduce the incidence of respiratory infections in the ultramarathon runners. To test their hypothesis, 20 runners were randomly assigned into two groups of 10 runners each. One group was given the same dose of vitamin C, in pill form, for 10 days before and 10 days after the race and the other group was given a sugar pill. Ten days after the race, the two groups were studied to determine how many of the runners in each group developed a respiratory infection. Neither the runners not the doctors examining them knew which treatment group they belonged to. Suppose the ultramarathon race all runners completed was held in Denver, CO (5280 feet above sea level). What is true about the results of this experiment?
The results may not be the same for ultramarathon runners participating in races at a different altitudes.
The bean pod mottle virus (BPMV) is a virus found in soybeans spread by the bean leaf beetle. Concerned with the health of his own field of soybeans, a soybean farmer decided to conduct a small study to compare pesticides. He had 5 acres of land, far from any trees to prevent any area getting less sunlight, that he separated into 30 plots and planted 40 soybean plants per plot. He then randomly chose 10 plots to receive his usual pesticide, 10 plots to receive a new organic pesticide, and the last 10 plots were left untreated (given no pesticide). Also, to maintain constant conditions across the field, each plot was watered equally by the same farmer and using the same equipment. Once the soybean season was over, the farmer recorded the proportion of infected soybean plants from the 40 plants in each of the 30 plots. This is an experiment.
True
non-response bias
When people choose not to participate in the survey, it is called
voluntary response sample
When people select themselves for a sample, it is called a(n)
Observational study
When researchers make no attempt to assign values of the variable to certain people, but instead simply observe them, this is called a(n)
Experiment
When researchers manipulate values of an explanatory variable or variables, this is called a(n)
blinding
When the experimenter and/or the subjects do not know which treatment they are receiving, this is called
experimental units
Who or what the experiment is performed on is called the
An ultramarathon is a foot race that is longer than 26.2 miles. Doctors have found that people who run an ultramarathon are at increased risk for developing respiratory infections after the race. Doctors believe that taking vitamin C the 10 days before and the 10 days after the race would reduce the incidence of respiratory infections in the ultramarathon runners. In a new experiment of 20 different runners, 10 male runners and 10 female runners were selected and each gender was randomly assigned into two groups of 5 runners each. One of each gender group was given the same dose of vitamin C, in pill form, for 10 days before and 10 days after the race and the other group was given a sugar pill. Ten days after the race, the four groups were studied to determine how many of the runners in each group developed a respiratory infection. In this experiment, gender is being used as a ________.
block
When first introduced, the Xbox video game system had some serious flaws. Numerous systems were over heating which would cause the game to crash after playing for a while. In order to correct the problem, experts suggested either adding an extra fan to disperse heat or installing one higher quality fan. To decide the best approach, a group of engineers at Microsoft conducted a study. Thirty Xbox machines were randomly selected from the assembly line, right before the usual fan was installed. Once selected, the engineers rolled a dice to decide which fan or fans to install in the machine. If they rolled 1 or 4, the machine received the old fan. If they rolled 2 or 5, the machine received two old fans. Finally, if they rolled a 3 or 6, the machine received the higher quality fan. This was done so that there were ten machines in each of the treatment groups. Once the Xbox machines were completely assembled, they were then taken to a large room keep at a constant 72 degrees Fahrenheit with 30 different stations setup in equally spaced distances across the room. Each station had the same style television and television stand. Once in their stations, all of the Xbox machines were run with the same graphic intensive game for as long as it took for the machine to overheat. The time until each machine overheats was recorded in minutes. In this study, which type(s) of randomization have been implemented?
both random assignment and random selection
An ultramarathon is a foot race that is longer than 26.2 miles. Doctors have found that people who run an ultramarathon are at increased risk for developing respiratory infections after the race. Doctors believe that taking vitamin C the 10 days before and the 10 days after the race would reduce the incidence of respiratory infections in the ultramarathon runners. To test their hypothesis, 20 runners were randomly assigned into two groups of 10 runners each. One group was given the same dose of vitamin C, in pill form, for 10 days before and 10 days after the race and the other group was given a sugar pill. Ten days after the race, the two groups were studied to determine how many of the runners in each group developed a respiratory infection. Neither the runners not the doctors examining them knew which treatment group they belonged to. What type of blinding was used in this experiment?
double binding
Subjective/personal
probability is based on a feeling or opinion.
The following excerpt is taken from an article that appeared in the Des Moines Register on Wednesday, September 25, 2002 titled "Aspirin- like drugs may cut Alzheimer's risk:" Taking aspirin and other anti-inflammatory medications for at least two years may reduce the risk of developing Alzheimer's disease, according to a study. The study, which enrolled 5,092 Utah residents 65 and older and followed them for several years, examined anti-inflammatory medications, including ibuprofen and naproxen. Patients taking an anti-inflammatory medication for at least two years developed Alzheimer's at roughly half the rate of non-users. The results were nearly as strong for those who used aspirin regularly. One drawback is that the study involved a community of primarily Mormon residents, who tend to live a more healthy lifestyle. What type of study was conducted?
prospective study
When first introduced, the Xbox video game system had some serious flaws. Numerous systems were over heating which would cause the game to crash after playing for a while. In order to correct the problem, experts suggested either adding an extra fan to disperse heat or installing one higher quality fan. To decide the best approach, a group of engineers at Microsoft conducted a study. Thirty Xbox machines were randomly selected from the assembly line, right before the usual fan was installed. Once selected, the engineers rolled a dice to decide which fan or fans to install in the machine. If they rolled 1 or 4, the machine received the old fan. If they rolled 2 or 5, the machine received two old fans. Finally, if they rolled a 3 or 6, the machine received the higher quality fan. This was done so that there were ten machines in each of the treatment groups. Once the Xbox machines were completely assembled, they were then taken to a large room keep at a constant 72 degrees Fahrenheit with 30 different stations setup in equally spaced distances across the room. Each station had the same style television and television stand. Once in their stations, all of the Xbox machines were run with the same graphic intensive game for as long as it took for the machine to overheat. The time until each machine overheats was recorded in minutes. Fill in the blanks: This experiment used __________ by having multiple Xbox machines in each treatment group. The experiment does not have ______________ because the entire experiment was not duplicated.
replication repeatability
