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Which of the following is a true statement? (A) If bias is present in a sampling procedure, it can be overcome by dramatically increasing the sample size. (B) There is no such thing as a "bad sample." (C) Sampling techniques that use probability techniques effectively eliminate bias. (D) Convenience samples often lead to undercoverage bias. (E) Voluntary response samples often underrepresent people with strong opinions.

In a \(1927-1932\) Western Electric Company study on the effect of lighting on worker productivity, productivity increased with each increase in lighting but then also increased with every decrease in lighting. If it is assumed that the workers knew that they were being observed and that a study was in progress, this is an example of (A) the effect of a treatment unit. (B) the placebo effect. (C) the control group effect. (D) sampling error. (E) voluntary response bias.

Two studies are run to compare the experiences of families living in high-rise public housing to those of families living in townhouse subsidized rentals. The first study interviews 25 families who have been in each government program for at least 1 year, while the second randomly assigns 25 families to each program and interviews them after 1 year. Which of the following is a true statement? (A) Both studies are observational studies because of the time period involved. (B) Both studies are observational studies because there are no control groups. (C) The first study is an observational study, while the second is an experiment. (D) The first study is an experiment, while the second is an observational study. (E) Both studies are experiments.

A study is made to determine whether taking AP Statistics in high school helps students achieve higher GPAs when they go to college. In comparing records of 200 college students, half of whom took AP Statistics in high school, it is noted that the average college GPA is higher for those 100 students who took AP Statistics than for those who did not. Based on this study, guidance counselors begin recommending AP Statistics for college-bound students. Which of the following is incorrect? (A) While this study indicates a relation, it does not prove causation. (B) There could well be a confounding variable responsible for the seeming relationship. (C) Self-selection here makes drawing the counselors' conclusion difficult. (D) A more meaningful study would be to compare an SRS from each of the two groups of 100 students. (E) This is an observational study, not an experiment.

Which of the following is incorrect? (A) Blocking is to experiment design as stratification is to sampling design. (B) By controlling certain variables, blocking can make conclusions more specific. (C) The paired comparison design is a special case of blocking. (D) Blocking results in increased accuracy because the blocks have smaller size than the original group. (E) In a randomized block design, the randomization occurs within the blocks.

In a study of successes and failures in adopting Common Core standards, a random sample of high school principals will be selected from each of the 50 states. Selected individuals will be asked a series of evaluative questions. Why is stratification used here? (A) To minimize response bias (B) To minimize nonresponse bias (C) To minimize voluntary response bias (D) Because each state is roughly representative of the U.S. population as a whole (E) To obtain higher statistical precision because variability of responses within a state is likely less than variability of responses found in the overall population

Which of the following is a true statement about sampling error? (A) Sampling error can be eliminated only if a survey is both extremely well designed and extremely well conducted. (B) Sampling error reflects natural variation between samples, is always present, and can be described using probability. (C) Sampling error is generally larger when the sample size is larger. (D) Sampling error implies an error, possibly very small, but still an error on the part of the surveyor. (E) Sampling error is higher when bias is present.

When the estrogen-blocking drug tamoxifen was first introduced to treat breast cancer, there was concern that it would cause osteoporosis as a side effect. To test this concern, cancer subjects were randomly selected and given tamoxifen, and their bone density was measured before and after treatment. Which of the following is a true statement? (A) This study was an observational study. (B) This study was a sample survey of randomly selected cancer patients. (C) This study was an experiment in which the subjects were used as their own controls. (D) With the given procedure, there cannot be a placebo effect. (E) Causation cannot be concluded without knowing the survival rates.

A consumer product agency tests miles per gallon for a sample of automobiles using each of four different octanes of gasoline. Which of the following is true? (A) There are four explanatory variables and one response variable. (B) There is one explanatory variable with four levels of response. (C) Miles per gallon is the only explanatory variable, but there are four response variables corresponding to the different octanes. D) There are four levels of a single explanatory variable. (E) Each explanatory level has an associated level of response.

To find out the average occupancy size of student-rented apartments, a researcher picks a simple random sample of 100 such apartments. Even after one follow-up visit, the interviewer is unable to make contact with anyone in 27 of these apartments. Concerned about nonresponse bias, the researcher chooses another simple random sample and instructs the interviewer to continue this procedure until contact is made with someone in a total of 100 apartments. The average occupancy size in the final 100-apartment sample is 2.78 . Is this estimate probably too low or too high? (A) Too low, because of undercoverage bias (B) Too low, because convenience samples overestimate average results (C) Too high, because of undercoverage bias (D) Too high, because convenience samples overestimate average results (E) Too high, because voluntary response samples overestimate average results