AP Stats: Chapter 4

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 randomly assigned 100 adult volunteers who suffer from allergies to two groups. They gave the new medication to the subjects in one group and an existing medication to the subjects in the other group. Forty-four percent of those in the treatment group and 28% of those in the control group reported a significant reduction in their allergy symptoms without any drowsiness. The experimental units are the:

100 adult volunteers

We wish to choose a simple random sample of size three from the following list of employees of a small company. To do this, we will use the numerical labels attached to the names below.1. Bechhofer 2. Brown 3. Ito 4. Kesten 5. Kiefer 6. Spitzer 7. Taylor 8. Wald 9. Weiss 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 sample you obtain is:

Bechhofer, Taylor, and Weiss

A poll conducted by the student newspaper asked, "Who do you believe will win the Ohio State Undergraduate Student Government election?" To vote, students had to access the student newspaper's Website and record their vote. Which of the following statements is true?

The results of the survey are unreliable because response to the survey was voluntary.

Which of the following is a method for improving the accuracy of a sample?

Use large sample sizes.

Mrs. De La Fe, a sportswriter, wants to know how strongly Orlando residents support the professional baseball team, the Orlando Rays. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. The intended population for this survey is

all residents of Orlando.

A news release for a diet product company reports: "We have good news for the 65 million Americans currently on a diet." Its study showed that people who lose weight can keep it off. The sample was twenty graduates of the company's program who endorse it in commercials. The results of the study are probably

biased, overstating the effectiveness of the diet. 1

A marine biologist wants to estimate the mean size of the barnacle Semibalanus balanoides on a stretch of rocky shoreline. To do so, he randomly selected twenty 10 by 10 square inch plots and measured the size of every barnacle in each plot. This is an example of

cluster sample

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a"treatment" (two cups of coffee) and all students in the 9:30 section are not permitted to have any caffeine before a mid-term exam. Unfortunately, any systematic difference between the two sections on the exam might be due to the fact that the 8:30 and 9:30 classes have different instructors. This is an example of

confounding

If changes in a response variable are due to the effects of the explanatory variable as well as the effects of another variable, and we cannot distinguish between these effects, we are said to have

confounding

To assess the opinion of students at the University of Minnesota about campus snow removal, a reporter for the student newspaper interviews the first 12 students he meets who are willing to express their opinion. The method of sampling used is:

convenience sampling.

The most important advantage of experiments over observational studies is that:

experiments can give better evidence of causation.

We wish to draw a sample of 5 without replacement from a population of 50 households. Suppose the households are numbered 01, 02, ..., 50, and suppose that the relevant line of the random number table is

households 11, 36, 23, 08, and 42

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 study would be double blind if

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

Frequently, telephone poll-takers call near dinner time (between 6 pm and 7 pm) because most people are athome them. This is an effort to avoid

nonresponse

A public opinion poll in Ohio wants to determine if registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of fifty registered voters from each county in the state and ask whether they approve or disapprove of the measure. This is an example of a:

stratified random sample

You want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association (the largest teachers' union) and mail a questionnaire to 2500 teachers chosen at random from this list. In all 1347 teachers return the questionnaire.The sample is:

the 1347 teachers who mail back the questionnaire.

Just before the presidential election of 1936, the magazine Literary Digest predicted—incorrectly, as it turned out—that Alf Landon would defeat Franklin Delano Roosevelt. Landon lost in a landslide. It turned out that the magazine had only polled its own subscribers, plus others from a list of automobile owners and a list of people who had telephone service. All three groups had higher than typical incomes during the Great Depression, This is an example of

undercoverage.

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, sowe 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.