Stat Chap 4 Test

A stratified random sample addresses the same issues as which of the following experimental designs?

a. A block design.

A candidate for mayor of Dallas calls 1,000 people chosen at random from the city telephone directory; 850 of them respond. What are the sampling frame and the sample in this example?

a. Sampling frame: the telephone directory. Sample: the 850 people who respond.

A television station is interested in predicting whether voters in its viewing area are in favor of offshore drilling. It asks its viewers to phone in and indicate whether they support/are in favor of or are opposed to this practice. Of the 2241 viewers who phoned in, 1574 (70%) were opposed to offshore drilling. The viewers who phoned in are

a. a voluntary response sample.

The intended population for this survey is

a. all residents of Lafayette.

A news release for a diet products company reports: "There's 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

a. biased, overstating the effectiveness of the diet.

An experiment was conducted by some students to explore the nature of the relationship between a person's heart rate (measured in beats per minute) and the frequency at which that person stepped up and down on steps of various heights. Three rates of stepping and two different step heights were used. A subject performed the activity (stepping at one of the three stepping rates at one of the two possible heights) for three minutes. Heart rate was then measured at the end of this period. The variables "stepping rate" and "step height" are the

a. factors.

In order to assess the effects of exercise This is a(n)

a. observational study.

You want to know the opinions of American school teachers The sample is

a. the 1347 teachers who mail back the questionnaire.

Researchers wish to determine if a new experimental medication will reduce symptoms The experimental units are the

b. 100 adult volunteers.

Which of the following best describes the inferences the researcher can make based in his results?

b. He can make inferences about the populations from which the samples were taken, but not about cause and effect

A local tax reform group polls the residents of the school district and asks the question, "Do you think the school board should stop spending taxpayers' money on non-essential arts programs in elementary schools?" The results of this poll are likely to

b. Underestimate support for arts programs because of nonsampling error.

To determine the proportion of each color of Peanut Butter M&M, you buy 10 1.69 ounce packages and count how many there are of each color. This is an example of

b. cluster sampling

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

b. cluster sampling.

The most important advantage of experiments over observational studies is that

b. experiments can give better evidence of causation.

A public opinion poll in Ohio wants to determine whether or not 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

b. stratified random sample.

Bechhofer, Brown, Ito The simple random sample is

c. Bechhofer, Taylor, Weiss.

Which of the following is not a major principle of good design for all experiments?

c. Blocking

A stratified random sample is appropriate when

c. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups.

A simple random sample of size n is defined to be

c. a sample of size n chosen in such a way that every set of n units in the population has an equal chance to be the sample actually selected.

A simple random sample is

c. a sample that gives every possible sample of the same size the same chance to be selected

The sampling frame is

c. all members of the National Education Association.

Does caffeine improve exam performance? Unfortunately, any systematic difference between the two sections on the exam mig

c. confounding.

In order to select a sample of undergraduate students in the United States, I select a simple random sample of four states. From each of these states, I select a simple random sample of two colleges or universities. Finally, from each of these eight colleges or universities, I select a simple random sample of 20 undergraduates. My final sample consists of 160 undergraduates. This is an example of

c. multistage sampling.

A farmer wishes to determine The brand of pellets is

c. the explanatory variable.

Another correct choice of labels for the 816 students is

d. Both (B) and (C) are correct.

Which of the following statements is true?

d. If we use another list of random digits to select the sample, the result obtained with the list actually used would be just as likely to be selected as any other set of three names.

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

d. This is a convenience sample. It will almost certainly overestimate the level of support among all Lafayette residents.

If the farmer had fed Kent pellets to an SRS of 5 pigs from litter A and an SRS of 5 pigs from litter B, with the remaining 10 pigs getting Moormans pellets, then he would have been using

d. a block design.

In order to assess the opinion of students at the University of Minnesota on 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

d. a convenience sample

A study sponsored by American Express Co. and the French government tourist office found that old stereotypes about French unfriendliness were not true. The respondents were more than 1000 Americans who have visited France more than once for pleasure over the past two years. The results of this study are probably

d. biased, overstating the extent to which the old stereotypes were not true.

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

d. nonresponse.

Sportswear The sample for the survey is

d. the 20 people who gave the sportswriter their opinion

You want to take an SRS of 50 of the 816 students The first three students in your sample have labels

e. 400, 769, 335.

Simple random sampling

e. None of the above.

Instead of giving all students in the 8:30 section two cups of coffee, students in the 8:30 section are randomly assigned to a treatment group (two cups of coffee. or a control group (two cups of decaffeinated coffee). The coffee is so bad that students cannot tell whether they are in the treatment or the control group. As it turns out, students in both groups do better on the exam than students in the 9:30 section, who weren't given anything. This could be the result of

a. the placebo effect.

A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested in a new upscale men's clothing store. From a list of all residential addresses in Laramie, the firm selects a simple random sample of 100 and mails a brief questionnaire to each. The chance that all 100 homes in a particular neighborhood in Laramie end up being the sample of residential addresses selected is

a. the same as for any other set of 100 residential addresses.

A 1992 Roper poll found that 22% of Americans say that the Holocaust may not have happened. The actual question asked in the poll was "Does it seem possible or impossible to you that the Nazi extermination of the Jews never happened?" and 22% responded possible. The results of this poll cannot be trusted because

b. the question is worded in a confusing manner.

In the late 1990's Scotland was considering independence from England. An opinion poll showed that 51% of Scots favor "independence." Another poll taken at the same time showed that only 34% favored being "separate" from England. The reason these results differ by so much is that

b. the wording of questions has a big effect on poll results.

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. The response variable is

b. which brand they prefer.

The eight students listed below are enrolled in a new honors course developed by the chemistry department. The sample you obtain is

c. Alvarez, Barlow, Salter, and Verducci.

Which of these statements about the table of random digits is true?

e. None of these is true.

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

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

The response variable in this study is

e. exam performance.

An example of a nonsampling error that can reduce the accuracy of a sample survey is

e. many members of the sample cannot be contacted.

The sample from Korea is a

e. stratified random sample.