AP STATS Unit 2

The study would be double blind if

. neither the volunteers nor the psychiatrist knew which treatment any person had received.

We wish to choose a simple random sample of size three from the following employees of a small company. 1. Bechhofer 4. Kesten 7. Taylor 2. Brown 5. Kiefer 8. Wald 3. Ito 6. Spitzer 9. Weiss To do this, we will use the numerical labels attached to the names above. We will also use the following list of random digits, reading the list from left to right, starting at the beginning of the list. 11793 20495 05907 11384 44982 20751 27498 12009 45287 71753 98236 66419 84533 The simple random sample is

Bechhofer, Taylor, Weiss.

Which of the following is not a major principle of experimental design?

Blocking

A group of college students believes that herbal tea has remarkable restorative powers. To test their theory, they make weekly visits to a local nursing home, visiting with residents, talking with them, and serving them herbal tea. After several months, many of the residents are more cheerful and healthy. Which of the following may be correctly concluded from this study?

The results of the study are not convincing because the effect of herbal tea is confounded with several other factors.

The newspaper asks you to comment on their survey of local opinion. You say:

The sampling method is biased. It will almost certainly overestimate the level of support among all Lafayette residents.

A census is

a sample that attempts to include the entire population.

Use the following to answer questions 2-4: A sportswriter wants to know how strongly Lafayette residents support the local minor league baseball team, the Lafayette Leopards. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. The population for this survey is

all residents of Lafayette.

The essential difference between an experiment and an observational study is that

an experiment imposes treatments on the subjects, but an observational study does not

A market research company wishes to find out whether the population of students at a university prefers brand A or brand B of instant coffee. A random sample of students is selected, and each one is asked to try brand A first and then brand B (or vice versa, with the order determined at random). They then indicate which brand they prefer. This is an example of

an experiment.

Bias in a sampling method is

any systematic error that tends to occur in the same direction every time you use this sampling method.

The reason that blocking (as in a randomized block design) is sometimes used in experimentation is to

eliminate confounding with another factor.

The most important advantage of experiments over observational studies is that

experiments can give better evidence of causation.

Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers give the new medication to fifty adult volunteers who suffer from allergies. Forty-four of these volunteers report a significant reduction in their allergy symptoms without any drowsiness. The experimental units are the

fifty adult volunteers.

In order to assess the effects of exercise on reducing cholesterol, a researcher sampled fifty people from a local gym who exercised regularly and fifty people from the surrounding community who did not exercise regularly. They all reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether or not subjects exercised regularly. This is a(n)

observational study.

In an experiment, an observed effect so large that it would rarely occur by chance is called

statistically significant.

The sample for the survey is

the 20 people who gave the sportswriter their opinion.

Twelve people who suffer from chronic fatigue syndrome volunteer to take part in an experiment to see if shark fin extract will increase one's energy level. Eight of the volunteers are men, and four are women. Half of the volunteers are to be given shark fin extract twice a day, and the other half are to be given a placebo twice a day. We wish to make sure that four men and two women are assigned to each of the treatments, so we decide to use a block design with the men forming one block and the women the other. A block design is appropriate in this experiment if

we believe men and women will respond differently to treatments.

Use the following to answer questions 13-14: One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other fifty are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of the depression. The factor in this study is

which treatment the volunteers receive.