Chapter 11-13
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- 1.In an experiment, if two variables are confounded, which of the following statements is true?
- A.
One of the variables must be lurking variables.
- B.
The variables will have a correlation coefficient greater than 0.5.
- C.
There is a clear indication that a placebo effect is present in the experiment.
- D.
The investigator cannot separate the effect of the variables on a response variable.
- E.
None of these is true.
- 2.In one study on the effect of niacin on cholesterol level, 100 subjects who acknowledged being long-time niacin takers had their cholesterol levels compared with those of 100 people who had never taken niacin. In a second study, 50 subjects were randomly chosen to receive niacin and 50 were chosen to receive a placebo.
- A.
The first study was a controlled experiment, while the second was an observational study.
- B.
The first study was an observational study, while the second was a controlled experiment.
- C.
Both studies were controlled experiments.
- D.
Both studies were observational studies.
- E.
Each study was part controlled experiment and part observational study.
- 3.
- A.
Yes, because each player has the same chance of being selected.
- B.
Yes, because each team is equally represented.
- C.
Yes, because this is an example of stratified sampling, which is a special case of simple random sampling.
- D.
No, because the teams are not chosen randomly.
- E.
No, because not each group of 58 players has the same chance of being selected.
- 4.A study is made to determine whether studying Latin helps students achieve higher scores on the verbal section of the SAT exam. In comparing records of 200 students, half of whom have taken at least 1 year of Latin, it is noted that the average SAT verbal score is higher for those 100 students who have taken Latin than for those who have not. Based on this study, guidance counselors begin to recommend Latin for students who want to do well on the SAT exam. Which of the following are true statements? I. While this study indicates a relation, it does not prove causation. II. There could well be a confounding variable responsible for the seeming relationship. III. Self-selection here makes drawing the counselors' conclusion difficult.
- A.
I and II
- B.
I and III
- C.
II and III
- D.
I, II and III
- E.
None of the above gives the complete set of true responses.
- 5.A nutritionist believes that having each player take a vitamin pill before a game enhances the performance of the football team. During the course of one season, each player takes a vitamin pill before each game, and the team achieves a winning season for the first time in several years. Is this an experiment or an observational study?
- A.
An experiment, but with no reasonable conclusion possible about cause and effect.
- B.
An experiment, thus making cause and effect a reasonable conclusion.
- C.
An observational study, because there was no use of a control group.
- D.
An observational study, but a poorly designed one because randomization was not used.
- E.
An observational study, thus allowing a reasonable conclusion of association but not of cause and effect.
- 6.Blocking is utilized to help
- A.
Organize the treatment and control groups.
- B.
Counteract the placebo effect.
- C.
Produce groups that are as similar as possible.
- D.
Replicate the experiment with more subjects.
- E.
Avoid the need for randomization.
- 7.Which of the following situations qualifies as an observational study?
- A.
The girls at your high school are surveyed to determine if they believe there is any sexual stereotyping in the school newspaper.
- B.
Two flowerpots are planted with the same type of seed. One is given 0.2 cups of water each day while the other is given 0.5 cups of water each day. At the end of one month, the growth of each plant is observed and measured.
- C.
A student flips a coin 100 times and records the number of heads.
- D.
None of these are observational studies.
- 8.
- A.
The is an example of a multi-stage cluster sample.
- B.
Results from the interviews cannot be used to infer responses of the population of interest.
- C.
The population of interest is the set of all high school principals in New England.
- D.
Not every subset of principals has the same chance of selection.
- E.
All of these statements are true.
- 9.The student council of your high school wants to conduct a survey regarding the dress code for school dances. You have advised them that it might be best to conduct a stratified random sample of the student body. Which of the following is not a valid stratified design? Assume the results of the separate samples will be combined into a single sample of the student body.
- A.
Two simple random samples are to be conducted: one of the boys in the student body and the other of the girls in the student body.
- B.
Four simple random samples are conducted: one in each of the four classes.
- C.
Two simple random samples are conducted in randomly selected homerooms: one of the boys in the selected homerooms and the other of the girls in the selected homerooms.
- D.
Two random samples are conducted: one of students whose GPA's are 2.5 or higher and the other of students whose GPA's are less than 2.5.
- E.
None of these statements is a valid design.
- 10.A personnel director at a large company studied the eating habits of employees by watching the movement of a selected group of employees at lunchtime. The purpose of the study was to determine the proportion of employees who buy lunch in the cafeteria, bring their own lunches, or go out to lunch. If the director were to include all of the employees in her study, she is performing a
- A.
Simple random sample
- B.
Quota sample
- C.
Convenience sample
- D.
Multi-stage cluster sample
- E.
Census
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