STAT 111 SEC 006 PRACTICE EXAM 1: SPRING 2007

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1 STAT 111 SEC 006 PRACTICE EXAM 1: SPRING You want to know the opinions of American schoolteachers 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 2,500 teachers chosen at random from this list. In all 1,347 teachers return the questionnaire. In this situation, the population of interest is A) the 1,347 teachers who mail back the questionnaire. B) the 2,500 teachers to whom you mailed the questionnaire. C) all members of the National Education Association. D) all American school teachers. E) all American school students. 2. A study at Yale Medical School investigated treatments for chronic cocaine abusers. Of the 72 subjects, all cocaine users who wanted to quit, 24 were assigned at random to each of three drugs: (a) desipramine, (b) lithium, (c) a placebo. After 6 weeks the subjects reported whether they had stayed off cocaine. This study is an example of A) an experiment. B) a sample survey. C) using available data. D) an observational study, but not a sample survey. 3. When Ann Landers asked her readers to tell her "if your sex life has gone downhill after marriage," more than 100,000 people responded. This is an example of A) a self-selected sample D) a dis-stratified sample. B) an observational sample E) the placebo effect. C) a stratified sample. 4. Which of the following is correct? A) Parameters describe sample characteristics. B) Parameters describe population characteristics. C) The population is a subset of the sample. D) Statistics must be based on a simple random sample. E) Parameter and statistic are two names for the same thing.

2 5. In 1995, the Gallup Poll asked a sample of 620 people whether their support of baseball had been affected by the players' strike; 248 people in the sample said "Yes." Assuming there is no bias, we can be 95% confident that the percent of all adults whose support of baseball was affected by the strike is between A) 37% and 43%. D) 55% and 65%. B) 56% and 64%. E) 36% and 44%. C) 35% and 45%. Want to stop smoking? Nicotine patches may help, and so may taking a drug that fights depression. A report in a recent issue of the New England Journal of Medicine describes a study of what works best. Here is part of the summary: Use of nicotine replacement therapies and the antidepressant bupropion helps people stop smoking. We conducted a double-blind, placebo-controlled comparison of sustained-release bupropion (244 subjects), a nicotine patch (244 subjects), bupropion and a nicotine patch (245 subjects), and placebo (160 subjects) for smoking cessation. Results. The abstinence rates at 12 months were 15.6 percent in the placebo group, as compared with 16.4 percent in the nicotine patch group, 30.3 percent in the bupropion group, and 35.5 percent in the group given bupropion and the nicotine patch. 6. The response variable in this experiment is A) the combination of drug (bupropion or placebo) and nicotine patch. B) 893 people who want to quit smoking. C) bupropion. D) whether or not a subject was able to abstain from smoking for a year. 7. An article in USA Today on August 9, 1999 said that "a nationally representative survey of 3,617 Americans" shows that "People who attend religious services at least once a month live significantly longer than those who don't." But churchgoers are more likely to be nonsmokers and to have good health habits. Does attending religious services cause longer life? A) Yes, because this study is a comparative experiment. B) We can't say; the effects of going to church are confounded with the effects of other behavior such as not smoking. C) Yes, because a sample survey with a large sample size will have a small margin of error. D) No, we can be sure that only physical habits like not smoking can affect how long we live.

3 8. When a sample survey asks people about use of illegal drugs, some people who use drugs will deny that they do because they fear that the information will be given to the police or employers. A) This is a sampling error that causes bias. B) This is a sampling error that increases variability. C) This is a nonsampling error that causes bias. D) This is a nonsampling error that increases variability. Set up for 9&10: Students in a large statistics class were randomly divided into two groups. The first group took the midterm exam with music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared. 9. In this experiment the response variable is A) the score on the midterm exam. B) whether or not music was playing during the exam. C) the placebo. D) the scores of the students on the final exam. E) a lurking variable. 10. In this experiment the explanatory variable is A) the score on the midterm exam. B) whether or not music was playing during the exam. C) the placebo. D) the scores of the students on the final exam. E) a lurking variable. 11. A Gallup Poll recently showed that 60 percent of Americans believe there is a hell. (The question was, "Do you believe there is a place where those who led bad lives and died without repentance are eternally damned?") The poll contacted 1,108 adults by telephone. The margin of sampling error was plus or minus four percentage points. Assume a 95% confidence level and no bias. From the information given above, you can make which of the following statements. (Note that 60 ± 4% is 56 percent to 64 percent.) A) Between 56 percent and 64 percent of the sample believe there is a hell. B) Between 56 percent and 64 percent of all American adults believe there is a hell. C) We are 95% confident (but not certain) that between 56% and 64% of the sample believe there is a hell. D) We are 95% confident (but not certain) that between 56% and 64% of all American adults believe there is a hell.

4 12. The Physicians' Health Study gave half of a group of 22,000 male M.D.'s aspirin. The other half received a placebo. After five years there were 189 heart attacks in the placebo group and 104 in the aspirin group. One of the response variables in the Physicians' Health Study was A) the 22,000 male M.D.'s. B) whether a subject took aspirin or a placebo. C) whether or not a subject had a heart attack. D) the 11,000 subjects who received aspirin. 13. Any institution that does research with human subjects must have an Institutional Review Board. This board reviews all planned research with human subjects in advance in order to A) be sure that the placebo effect is accounted for. B) be sure that the researchers have published in reputable journals in the past. C) be sure that the research obeys all the standards that protect the human subjects from harm. D) be sure that tables of random digits have been properly used in assigning subjects to treatments. E) all of the above. 14. In one of the first attempts to discover the speed of light, Simon Newcomb in 1882 made 66 measurements of the time light takes to travel between the Washington Monument and his laboratory on the Potomac River. Why did Newcomb repeat his measurement 66 times and take the average of the 66 as his final result? A) Averaging several measurements reduces any bias that is present in his instruments. B) The average of several measurements is more reliable (less variable) than a single measurement. C) Even if a measuring process is not valid, averaging several measurements made by this process will be valid. D) Both (A) and (B) but not (C). E) All of (A), (B), and (C). 15. The diameter of a metal rod was measured 8 times and the results in millimeters were 31.7, 31.7, 31.8, 31.7, 31.7, 31.8, 31.8 The true diameter of the rod is 29.2 millimeters. The measurement process appears to A) be biased and unreliable. C) be unbiased but unreliable. B) be reliable but somewhat biased. D) be unbiased and reliable. 16. In January of 1997, the price of Intel common stock rose from $131 per share to $162 per share. What percent increase is this? A) 19.1% B) 23.7% C) 80.9% D) 123.7%

5 17. An ad for a new heartburn treatment says that it "reduces heartburn by 300 percent." What does this mean? A) It means that there is 3 times as much heartburn before using the treatment as there is after using it. B) It means there is only seven-tenths as much heartburn after using the treatment, because 300/1000 = 0.3, or three-tenths. C) It's nonsense, because removing 100 percent of the heartburn already removes all of it. D) It's nonsense, because heartburn is a categorical variable, so percents don't make sense. E) It's nonsense because percents only make sense for counts, and amount of heartburn isn't a count. 18. Following are data on the populations and numbers of death row prisoners for several states. State Population Death Row Prisoners (thousands) California 28, Florida 12, Illinois 11, Nevada 1, Which state has the highest number of death row prisoners relative to the size of its population? A) California B) Florida C) Illinois D) Nevada Set up for 19 & 20: You have invented a drug that you think will relieve anxiety and help students score better on exams. You want to test the drug on a group of statistics students who are about to take their final exam. 19. You will give some students your new drug and others a dummy pill. Why? A) To avoid the bad effects of voluntary response. B) To avoid confounding with the placebo effect. C) To allow you to decide who gets the drug. D) To allow students to choose whether they want to take the drug. E) To allow you to have 95% confidence. 20. What is a reasonable response variable for the experiment? A) Whether a student received the drug or the dummy pill. B) The chemical composition of your drug. C) A student's overall GPA. D) A student's score on a statistics final exam. E) Whether a student liked the taste of the drug.