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Chapter 11: Q11-2-4BSC (page 533)
Is the hypothesis test described in Exercise 1 right tailed, left-tailed, or two-tailed? Explain your choice.
The hypothesis test is right-tailed.
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The table below includes results from polygraph (lie detector) experiments conducted by researchers Charles R. Honts (Boise State University) and Gordon H. Barland (Department of Defense Polygraph Institute). In each case, it was known if the subject lied or did not lie, so the table indicates when the polygraph test was correct. Use a 0.05 significance level to test the claim that whether a subject lies is independent of the polygraph test indication. Do the results suggest that polygraphs are effective in distinguishing between truths and lies?
| |||
No (Did Not Lie) | Yes (Lied) | ||
| 15 | 42 | |
| 32 | 9 | |
In a clinical trial of the effectiveness of echinacea for preventing
colds, the results in the table below were obtained (based on data from “An Evaluation of Echinacea Angustifoliain Experimental Rhinovirus Infections,” by Turner et al., NewEngland Journal of Medicine,Vol. 353, No. 4). Use a 0.05 significance level to test the claim that getting a cold is independent of the treatment group. What do the results suggest about the
effectiveness of echinacea as a prevention against colds?
| |||||
Placebo | Echinacea: 20% Extract | Echinacea: 60% Extract | |||
Got a Cold | 88 | 48 | 42 | ||
Did Not Get a Cold | 15 | 4 | 10 | ||
Exercises 1–5 refer to the sample data in the following table, which summarizes the last digits of the heights (cm) of 300 randomly selected subjects (from Data Set 1 “Body Data” in Appendix B). Assume that we want to use a 0.05 significance level to test the claim that the data are from a population having the property that the last digits are all equally likely.
Last Digit | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
Frequency | 30 | 35 | 24 | 25 | 35 | 36 | 37 | 27 | 27 | 24 |
If using a 0.05 significance level to test the stated claim, find the number of degrees of freedom.
In Exercises 5–20, conduct the hypothesis test and provide the test statistic and the P-value and, or critical value, and state the conclusion.
Police Calls Repeat Exercise 11 using these observed frequencies for police calls received during the month of March: Monday (208); Tuesday (224); Wednesday (246); Thursday (173); Friday (210); Saturday (236); Sunday (154). What is a fundamental error with this analysis?
A case-control (or retrospective) study was conductedto investigate a relationship between the colors of helmets worn by motorcycle drivers andwhether they are injured or killed in a crash. Results are given in the table below (based on datafrom “Motorcycle Rider Conspicuity and Crash Related Injury: Case-Control Study,” by Wellset al., BMJ USA,Vol. 4). Test the claim that injuries are independent of helmet color. Shouldmotorcycle drivers choose helmets with a particular color? If so, which color appears best?
| |||||||
Black | White | Yellow/Orange | Red | Blue | |||
Controls (not injured) | 491 | 377 | 31 | 170 | 55 | ||
Cases (injured or killed) | 213 | 112 | 8 | 70 | 26 | ||
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