Question 1

The reason that block designs are sometimes used in experimentation is to

Accepted Answer

A)  prevent the placebo effect. 
B)  allow double-blinding. 
C)  reduce sampling variability. 
D)  eliminate sampling variability. 
A)  prevent the placebo effect. 
B)  allow double-blinding. 
C)  reduce sampling variability. 
D)  eliminate sampling variability. C

Question 2

Does Stay Bright nail polish remain on fingernails longer than Acme nail polish? You design an experiment to find out. A random sample of people was selected to wear both nail polishes. Which hand received which polish was determined randomly. After one week, the difference in the quality of the nail polish of each subject is evaluated. What type of experimental design is this?

Accepted Answer

A)  This is a nonrandomized design. 
B)  This is a matched pairs design. 
C)  This is a completely randomized design with one factor. 
D)  This is a completely randomized design with two factors. 
E)  This is an observational study. 
A)  This is a nonrandomized design. 
B)  This is a matched pairs design. 
C)  This is a completely randomized design with one factor. 
D)  This is a completely randomized design with two factors. 
E)  This is an observational study. B

Question 3

It is difficult to establish the causal link between cigarette smoking and lung cancer because

Accepted Answer

A)  random allocation of subjects to smoking is unethical. 
B)  observational studies generally cannot rule out confounding. 
C)  those who choose to smoke may be genetically at greater risk for lung cancer than those who don't choose to smoke. 
D)  experiments done on animals may not be valid for humans. 
E)  All of the above 
A)  random allocation of subjects to smoking is unethical. 
B)  observational studies generally cannot rule out confounding. 
C)  those who choose to smoke may be genetically at greater risk for lung cancer than those who don't choose to smoke. 
D)  experiments done on animals may not be valid for humans. 
E)  All of the above E

Question 4

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.
The study design looked like this:  
Treatment 2 was a dummy pill. Such a dummy treatment is called a

Accepted Answer

A)  double-blind technique. 
B)  categorical variable. 
C)  nonsampling error. 
D)  placebo. 
E)  comparative. 
A)  double-blind technique. 
B)  categorical variable. 
C)  nonsampling error. 
D)  placebo. 
E)  comparative.

Question 5

A music professor offers his 40 students the option of coming to an additional rehearsal session the week before their juries (musical final exams.) In order to decide whether these extra sessions actually help students, he keeps track of who attends them and compares their jury scores to those of students who did not schedule extra sessions.
This study is a(n):

Accepted Answer

A)  observational study. 
B)  nonrandomized experiment. 
C)  completely randomized experiment. 
D)  randomized block design. 
E)  matched pairs design. 
A)  observational study. 
B)  nonrandomized experiment. 
C)  completely randomized experiment. 
D)  randomized block design. 
E)  matched pairs design.

Question 6

Two essential features of all statistically designed experiments are that they

Accepted Answer

A)  compare several treatments and use the double-blind method. 
B)  compare several treatments and use chance to assign subjects to treatments. 
C)  always have a placebo group and use the double-blind method. 
D)  use a block design and use chance to assign subjects to treatments. 
A)  compare several treatments and use the double-blind method. 
B)  compare several treatments and use chance to assign subjects to treatments. 
C)  always have a placebo group and use the double-blind method. 
D)  use a block design and use chance to assign subjects to treatments.

Question 7

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.
The study design looked like this:  
In order to avoid unconscious bias, neither the subjects not the doctors who examined them knew whether a particular subject was taking vitamins or dummy pills. This is called

Accepted Answer

A)  the placebo effect. 
B)  the double-blind technique. 
C)  the retrospective method. 
D)  stratified sampling. 
E)  internal validity. 
A)  the placebo effect. 
B)  the double-blind technique. 
C)  the retrospective method. 
D)  stratified sampling. 
E)  internal validity.

Question 8

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.
The study design looked like this:  
A weakness of this study is that

Accepted Answer

A)  it isn't clear that the results apply to women. 
B)  observational studies give only weak evidence for causation. 
C)  the people who took vitamins may have had other good habits. 
D)  the response is measured in a biased way. 
E)  nonsampling errors may be large. 
A)  it isn't clear that the results apply to women. 
B)  observational studies give only weak evidence for causation. 
C)  the people who took vitamins may have had other good habits. 
D)  the response is measured in a biased way. 
E)  nonsampling errors may be large.

Question 9

A music professor offers his 40 students the option of coming to an additional rehearsal session the week before their juries (musical final exams.) In order to decide whether these extra sessions actually help students, he keeps track of who attends them and compares their jury scores to those of students who did not schedule extra sessions.
In this study, a difference was found between the scores of students who scheduled the extra sessions and those of students who didn't attend (higher average for students with extra sessions). Does this study give evidence that attending the review session leads to higher grades on their juries?

Accepted Answer

A)  Yes, because the study included both students who attended the review session and those who did not. 
B)  Yes, because the number of subjects in the study was large. 
C)  Yes, because the study relied on a common final exam for everyone. 
D)  No, because the students chose whether they attended the review session or not. 
E)  No, because the students in the study were not blinded. 
A)  Yes, because the study included both students who attended the review session and those who did not. 
B)  Yes, because the number of subjects in the study was large. 
C)  Yes, because the study relied on a common final exam for everyone. 
D)  No, because the students chose whether they attended the review session or not. 
E)  No, because the students in the study were not blinded.

Question 10

A park ranger at Shenandoah National park wants to know if visitors to our country's national parks can properly identify poison ivy. Over the course of a month, she shows several plant varieties to 30 randomly selected visitors per week, and 74 of them correctly identify the poison ivy. The biggest potential weakness of experiments is that:

Accepted Answer

A)  experiments do not give good evidence for cause and effect. 
B)  experiments only work when one can give a placebo. 
C)  it can be hard to generalize conclusions beyond the actual subjects to a wider population. 
D)  informed consent is often not possible. 
A)  experiments do not give good evidence for cause and effect. 
B)  experiments only work when one can give a placebo. 
C)  it can be hard to generalize conclusions beyond the actual subjects to a wider population. 
D)  informed consent is often not possible.

Question 11

Which of the following statements about a randomized block design with two treatments is not true?

Accepted Answer

A)  Every subject has a 50/50 chance of being given the first treatment. 
B)  Block A is chosen randomly from among the available subjects. 
C)  In every block, some subjects are assigned the first treatment and some the second treatment. 
D)  Treatments are assigned randomly within each block. 
A)  Every subject has a 50/50 chance of being given the first treatment. 
B)  Block A is chosen randomly from among the available subjects. 
C)  In every block, some subjects are assigned the first treatment and some the second treatment. 
D)  Treatments are assigned randomly within each block.

Question 12

Randomization in experimental design is used to

Accepted Answer

A)  control for the response variable. 
B)  avoid confounding. 
C)  avoid the placebo effect. 
D)  implement the double-blind technique. 
A)  control for the response variable. 
B)  avoid confounding. 
C)  avoid the placebo effect. 
D)  implement the double-blind technique.

Question 13

A study of a drug to prevent hair loss showed that 86% of the men who took it maintained or increased the amount of hair on their heads. But so did 42% of the men in the same study who took a placebo instead of the drug. This is an example of

Accepted Answer

A)  a sampling error: The study should not have included men whose hair grew without the drug. 
B)  the placebo effect. 
C)  an error in calculating percentages. 
D)  failure to use the double-blind idea. 
A)  a sampling error: The study should not have included men whose hair grew without the drug. 
B)  the placebo effect. 
C)  an error in calculating percentages. 
D)  failure to use the double-blind idea.

Question 14

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared.
To improve the design of this experiment, one part of it should be done in a blind way. That is, we should:

Accepted Answer

A)  not tell volunteers in advance what treatment they may be exposed to. 
B)  not allow the volunteers to find out their flexibility scores. 
C)  tell all of the volunteers who meditate they will get a gym membership if they work very hard on the flexibility test. 
D)  be sure that the person measuring the volunteers' flexibility doesn't know which ones meditated and which ones didn't. 
A)  not tell volunteers in advance what treatment they may be exposed to. 
B)  not allow the volunteers to find out their flexibility scores. 
C)  tell all of the volunteers who meditate they will get a gym membership if they work very hard on the flexibility test. 
D)  be sure that the person measuring the volunteers' flexibility doesn't know which ones meditated and which ones didn't.

Question 15

To control for the possible lurking variables when assigning subjects to the experiment's treatments, use:

Accepted Answer

A)  a placebo and double blinding. 
B)  blocking and randomization. 
C)  probability sampling and confounding. 
D)  explanatory and response variables. 
A)  a placebo and double blinding. 
B)  blocking and randomization. 
C)  probability sampling and confounding. 
D)  explanatory and response variables.

Question 16

A scientist is designing a clinical trial to test the effect of online chat counseling with migraine sufferers as a supplementary treatment in combating their migraines. Migraine sufferers will have access to counselors via online chat software; the scientist plans to see whether their migraine pain has been reduced after six weeks.
Preliminary information suggests that the effect of (face-to-face) counseling is larger for migraine sufferers who are women than men. Knowing this, the scientist would probably use a:

Accepted Answer

A)  stratified random sample. 
B)  completely randomized design. 
C)  block design, with counseling and no counseling as the blocks. 
D)  block design, with women and men as the blocks. 
A)  stratified random sample. 
B)  completely randomized design. 
C)  block design, with counseling and no counseling as the blocks. 
D)  block design, with women and men as the blocks.

Question 17

A recent medical study found that people who drink more than four cups of coffee a day have more heart attacks than people who drink less coffee or no coffee. This led some doctors to suspect that coffee may be a contributing factor in causing heart attacks. However, more careful analysis of the data showed that heavy coffee drinkers tend to smoke more than other people. This is an example of

Accepted Answer

A)  the placebo effect. 
B)  response error. 
C)  the double-blind technique. 
D)  a completely randomized design. 
E)  confounding. 
A)  the placebo effect. 
B)  response error. 
C)  the double-blind technique. 
D)  a completely randomized design. 
E)  confounding.

Question 18

Medical experiments, such as one to compare aspirin with a placebo for preventing heart attacks, are often double-blind. This means that

Accepted Answer

A)  neither the subject nor the doctors know which treatment the patient received. 
B)  subjects choose which treatment they get, but do not tell the doctors. 
C)  the doctors choose which treatment to give each subject, but do not tell the subjects. 
D)  subjects are not told either their treatment or their medical condition. 
E)  all individual data are kept confidential. 
A)  neither the subject nor the doctors know which treatment the patient received. 
B)  subjects choose which treatment they get, but do not tell the doctors. 
C)  the doctors choose which treatment to give each subject, but do not tell the subjects. 
D)  subjects are not told either their treatment or their medical condition. 
E)  all individual data are kept confidential.

Question 19

A scientist is designing a clinical trial to test the effect of online chat counseling with migraine sufferers as a supplementary treatment in combating their migraines. Migraine sufferers will have access to counselors via online chat software; the scientist plans to see whether their migraine pain has been reduced after six weeks.
The subjects would obviously know whether or not they were given access to the counseling. What experimental technique does this eliminate?

Accepted Answer

A)  informed consent 
B)  randomization 
C)  blinding 
D)  confounding 
A)  informed consent 
B)  randomization 
C)  blinding 
D)  confounding

Question 20

You work for an agricultural supply company that is investigating a new fertilizer for soybeans. You have been asked to design an experiment to compare the effectiveness of three different application amounts of the fertilizer to find the optimal amount. Each field of soybeans will be fertilized with one of the application amounts (to be determined randomly). You think there may be large differences among different farms because of soil quality. Because of these differences, you should use a

Accepted Answer

A)  completely randomized design. 
B)  categorical variable. 
C)  block design. 
D)  matched pairs design. 
E)  multistage sample. 
A)  completely randomized design. 
B)  categorical variable. 
C)  block design. 
D)  matched pairs design. 
E)  multistage sample.

The reason that block designs are sometimes used in experimentation is to

It is difficult to establish the causal link between cigarette smoking and lung cancer because

Two essential features of all statistically designed experiments are that they

Which of the following statements about a randomized block design with two treatments is not true?

Randomization in experimental design is used to

A study of a drug to prevent hair loss showed that 86% of the men who took it maintained or increased the amount of hair on their heads. But so did 42% of the men in the same study who took a placebo instead of the drug. This is an example of

To control for the possible lurking variables when assigning subjects to the experiment's treatments, use:

Medical experiments, such as one to compare aspirin with a placebo for preventing heart attacks, are often double-blind. This means that

Where Do Data Come From

Samples, Good and Bad

What Do Samples Tell Us

Sample Surveys in the Real World

Experiments, Good and Bad

Data Ethics

Measuring

Do the Numbers Make Sense

Graphs, Good and Bad

Displaying Distributions With Graphs

Normal Distributions

Describing Relationships: Scatterplots and Correlation

Describing Relationships: Regression, Prediction, and Causation

The Consumer Price Index and Government Statistics

Thinking About Chance

Probability Models

Simulation

The House Edge: Expected Values

What Is a Confidence Interval

What Is a Test of Significance

Use and Abuse of Statistical Inference

Two-Way Tables and the Chi-Square Test

Filters

Exam 6: Experiments in the Real World

The reason that block designs are sometimes used in experimentation is to

It is difficult to establish the causal link between cigarette smoking and lung cancer because

Two essential features of all statistically designed experiments are that they

Which of the following statements about a randomized block design with two treatments is not true?

Randomization in experimental design is used to

A study of a drug to prevent hair loss showed that 86% of the men who took it maintained or increased the amount of hair on their heads. But so did 42% of the men in the same study who took a placebo instead of the drug. This is an example of

To control for the possible lurking variables when assigning subjects to the experiment's treatments, use:

Medical experiments, such as one to compare aspirin with a placebo for preventing heart attacks, are often double-blind. This means that

Where Do Data Come From

Samples, Good and Bad

What Do Samples Tell Us

Sample Surveys in the Real World

Experiments, Good and Bad

Data Ethics

Measuring

Do the Numbers Make Sense

Graphs, Good and Bad

Displaying Distributions With Graphs

Normal Distributions

Describing Relationships: Scatterplots and Correlation

Describing Relationships: Regression, Prediction, and Causation

The Consumer Price Index and Government Statistics

Thinking About Chance

Probability Models

Simulation

The House Edge: Expected Values

What Is a Confidence Interval

What Is a Test of Significance

Use and Abuse of Statistical Inference

Two-Way Tables and the Chi-Square Test

Filters