10 questions

23 minutes

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1. Which of the following can affect the value of the correlation r?

2. The American Medical Association (AMA) wishes to determine the percentage of obstetricians who are considering leaving the profession because of the rapidly increasing number of lawsuits against obstetricians. The AMA would like an answer to within ±3% at the 95% confidence level. Which of the following should be used to find the sample size (n) needed?

3. Suppose you did 10 independent tests of the form H0: μ = 25 versus Ha: μ < 25, each at the α = 0.05 significance level. What is the probability of committing a Type I error and incorrectly rejecting a true H0 with at least one of the 10 tests?

4. Which of the following sets has the smallest standard deviation? Which has the largest?

I.1, 2, 3, 4, 5, 6, 7

II.1, 1, 1, 4, 7, 7, 7

III.1, 4, 4, 4, 4, 4, 7

5. A researcher plans a study to examine long-term confidence in the U.S. economy among the adult population. She obtains a simple random sample of 30 adults as they leave a Wall Street office building one weekday afternoon. All but two of the adults agree to participate in the survey. Which of the following conclusions is correct?

6. Which among the following would result in the narrowest confidence interval?

7. Consider the following three scatterplots:

What is the relationship among r1, r2, and r3, the correlations associated with the first, second, and third scatterplots, respectively?

8. There are two games involving flipping a fair coin. In the first game you win a prize if you can throw between 45% and 55% heads. In the second game you win if you can throw more than 80% heads. For each game would you rather flip the coin 30 times or 300 times?

9. City planners are trying to decide among various parking plan options ranging from more on-street spaces to multilevel facilities to spread-out small lots. Before making a decision, they wish to test the downtown merchants' claim that shoppers park for an average of only 47 minutes in the downtown area. The planners have decided to tabulate parking durations for 225 shoppers and to reject the merchants' claim if the sample mean exceeds 50 minutes. If the merchants' claim is wrong and the true mean is 51 minutes, what is the probability that the random sample will lead to a mistaken failure to reject the merchants' claim? Assume that the standard deviation in parking durations is 27 minutes.

10. Consider the following parallel boxplots indicating the starting salaries (in thousands of dollars) for blue collar and white collar workers at a particular production plant:

Which of the following is a correct conclusion?