326 CHAPTER 7 Estimating Parameters and Determining Sample Sizes b. Based on his theory of genetics, Mendel expected that 75% of the offspring peas would be green. Given that the percentage of offspring green peas is not 75%, do the results contradict Mendel’s theory? Why or why not? 19. Tennis Challenges In a recent U. S. Open tennis tournament, women playing singles matches used challenges on 137 calls made by the line judges. Among those challenges, 33 were found to be successful with the call overturned. a. Construct a 99% confidence interval for the percentage of successful challenges. b. Compare the result from part (a) to this 99% confidence interval for the percentage of successful challenges made by the men playing singles matches: 28.7% 6 p 6 44.7%. Does it appear that either gender is more successful than the other? 20. OxyContin The drug OxyContin (oxycodone) is used to treat pain, but it is dangerous because it is addictive and can be lethal. In clinical trials, 227 subjects were treated with OxyContin and 52 of them developed nausea (based on data from Purdue Pharma L.P.). a. Construct a 95% confidence interval estimate of the percentage of OxyContin users who develop nausea. b. Compare the result from part (a) to this 95% confidence interval for 5 subjects who developed nausea among the 45 subjects given a placebo instead of OxyContin: 1.93% 6 p 6 20.3%. What do you conclude? 21. Touch Therapy When she was 9 years of age, Emily Rosa did a science fair experiment in which she tested professional touch therapists to see if they could sense her energy field. She flipped a coin to select either her right hand or her left hand, and then she asked the therapists to identify the selected hand by placing their hand just under Emily’s hand without seeing it and without touching it. Among 280 trials, the touch therapists were correct 123 times (based on data in “A Close Look at Therapeutic Touch,” Journal of the American Medical Association, Vol. 279, No. 13). a. Given that Emily used a coin toss to select either her right hand or her left hand, what proportion of correct responses would be expected if the touch therapists made random guesses? b. Using Emily’s sample results, what is the best point estimate of the therapists success rate? c. Using Emily’s sample results, construct a 99% confidence interval estimate of the proportion of correct responses made by touch therapists. d. What do the results suggest about the ability of touch therapists to select the correct hand by sensing an energy field? 22. Internet Use A random sample of 5005 adults in the United States includes 751 who do not use the Internet (based on three Pew Research Center polls). Construct a 95% confidence interval estimate of the percentage of U.S. adults who do not use the Internet. Based on the result, does it appear that the percentage of U.S. adults who do not use the Internet is different from 48%, which was the percentage in the year 2000? 23. Job Interviews In a Harris poll of 514 human resource professionals, 45.9% said that body piercings and tattoos were big personal grooming red flags. a. Among the 514 human resource professionals who were surveyed, how many of them said that body piercings and tattoos were big personal grooming red flags? b. Construct a 99% confidence interval estimate of the proportion of all human resource professionals believing that body piercings and tattoos are big personal grooming red flags. c. Repeat part (b) using a confidence level of 80%. d. Compare the confidence intervals from parts (b) and (c) and identify the interval that is wider. Why is it wider?
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