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CHAPTER 24 SOLUTIONS AND MINI-PROJECT NOTES CHAPTER 24 SIGNIFICANCE, IMPORTANCE AND UNDETECTED DIFFERENCES EXERCISE SOLUTIONS 24.1 a. Yes. b. No, the magnitude wasn't much different in a practical sense, but the large sample sizes led to a statistically significant difference. c. A statistically significant difference indicates that the difference in the population is not zero but does not indicate that it has any practical significance. The meaning should be clarified when the word is used. 24.2 a. If the researchers started out with the idea that Internet use would either increase depression or not have an effect on it, then it would be appropriate to use one-sided tests. If they originally wanted to see whether or not Internet use had an impact on depression by either increasing or decreasing it, two-sided tests would be appropriate. b. A type 1 error would occur if Internet use was not associated with greater loneliness, but the researchers concluded that it was. Since they did indeed make that conclusion, this is the type of error that could have been committed in this study. A type 2 error would occur if Internet use was associated with greater loneliness but the researchers failed to find the association. 24.3 a. A type 1 error is that the vaccine is not effective but the testing goes forward, which would not be too serious. A type 2 error is more serious; the vaccine is effective but testing does not take place and it is shelved. b. The tests on the small group may not have had enough power to detect the effectiveness of the vaccine, if it exists. 24.4 a. It would be 3(1.637) = 4.911. b. Null : There is no relationship between gender and driving after drinking in the population. Alternative : There is a relationship between them. The alternative would now be chosen because 0.03 is less than 0.05. c. The power would be higher with the larger sample size. 24.5
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This note was uploaded on 10/15/2011 for the course STAT 100 at Pennsylvania State University, University Park.

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