The fact that placebos work means that medical studies must take special care to show that a new treatment is not just a placebo. Answer True /False .
2. In a double blind experiment only the people who work with the experiment know which treatment each subject is receiving. Answer True /False
3 In a completely randomized experimental design, all the experimental subjects are allocated at random among all the treatments. Answer True/False

4 A block is a group of experimental subjects that are known before the experiment to be similar in some way that is expected to affect the response to the treatments. Answer True/False
5 IN a block design, the random assignment of subjects to treatments is carried out for all subjects at the same time. Answer True /False
6 A completely randomized designt divides all the subjects among all the treatments in one randomization.

Answer True /False
7 Block designs form blocks of simipar subjects and assign treatments at random separately in each block True False Answer True/ False
8 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. Bud so did 42% of the men in the same study who took a placebo instead of the drug. This is an example of
A. a sampling error: the study should not have included men whose hair grew without the drug
B. the placebo effect: a treatment often works if you believe that will work

C. an error in calculating percentages
D. failure to use the double blind data
9 Do doctors in managed care plans give less charity care? Researchers chose 60 communities at random, then chose doctors at random in each community. In all, they interviewed 10,881 doctors. Overall, 77.#% of the doctors said they had given some care free or at reduced rates because of the patients financial need in the month before the interview. Doctors who received at least 85% of their practice income from managed care plans were significantly less likely than other doctors to provide charity care.
The study design appears to be
A. a completely randomized experimental design

B. a block experimental design
C. a simple random sample
D. a multistage random sample .
10. Students is a large statistic class were divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared The study design for this experiment is called
A. a simple random sample design

B. a randomized blocks design
C. a matched pairs design
D. a completely randomized design
E. an observational study
11 Students is a large statistic class were divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared The experiment was not double blind because
A. students were allowed to keep their eyes open while taking the exam

B. The exam was too long
C. the students knew whether or not music was playing while they were taking the exam
D. some of the students did not study for the exam
E. students were randomized into the two groups .
12. Students is a large statistic class were divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared To improve the design of this experiment, one part of it should be done in a blind way. That is, we should

A. make the students take the exam in a dark room
B. let the students in the music group have extra time for the exam if they need it
C. not allow the students to find out their grades on the exam
D. tell all of the students that they will receive a grade of A on the exam if they agree to participate
E. be sure that the person grading the exam does not know which students listened to music and which did not.

13 An experiment compares two brands of automobile tires. Each of a number of cars is equipped with one tire of each brand on a rear wheel (the order is randomized from car to car) and tread wear is measured periodically. this is called a Answer
A. simple random sample
B. stratified random sample
C. completely randomized design
D. matched pairs design
E. double blind design
14 The reason that block designs are sometimes used in experimentation is to
A. prevent the placebo effect
B. allow double blinding
C. reduce sampling variability
E. eliminate sampling variability

15 A recent medical study found that people who drink more than 4 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
A. Answer the placebo effect
B. response error
C. the double blind technique
D. a completely randomized design
E. confounding
16 Two essential features of all statistically designed experiments are
A. compare several treatments; use the double blind method
B. compare several treatments; use chance to assign subjects to treatments
C. always have a placebo group; use the double blind method
D. use a block design; use chance to assign subjects to treatments
17. The most important principles of statistical design of experiments are:

A. randomization and comparison of several treatments
B. randomization and the double blind technique
C. random sampling and sampling distributions
D. confidence intervals and comparison of several treatments
E. margin of error and random sampling .
18. Does taking vitamins prevent colon cancer? A study assigned 864 subjects at random to four groups. One group took beta carotene, another took vitamins C and E, a third took all three, and the fourth r4oup took only a dummy pill. After four years, there was no difference among the group in the formation of polyps in the colon that precede cancer. The dummy pill given to the fourth group is called
A. a placebo
B. a double blind
C. a response variable
D. a comparative
19 Does taking vitamins prevent colon cancer? A study assigned 864 subjects at random to four groups. One group took beta carotene, another took vitamins C and E, a third took all three, and the fourth r4oup took only a dummy pill.

After four years, there was no difference among the group in the formation of polyps in the colon that precede cancer. Neither the subjects nor the medical personnel who worked with them knew what any subject s pills contained. We say that the study was
A. double blind
B. comparative
C. placebo
D. controlled
20 A double blind experiment was conducted to evaluate the effectiveness of the Salk polio vaccine. The purpose of keeping the diagnosing physicians ignorant of the treatment status of the experimental subjects was to

A. eliminate grounds for malpractice suits
B. ensure that subjects were randomly assigned to treatments
C. eliminate a possible source of bias
D. make sure nobody is harmed
F. prevent stratification of the experiment