766 APPENDIX D Answers to Odd-Numbered Section Exercises, plus Answers to All Chapter Quick Quizzes, Chapter Review Exercises, and Cumulative Review Exercises Chapter 1 Answers Section 1-1 1. The respondents are a voluntary response sample or a self-selected sample. Because those with strong interests in the topic are more likely to respond, it is very possible that their responses do not reflect the opinions or behavior of the general population. 3. Statistical significance is indicated when methods of statistics are used to reach a conclusion that a treatment is effective, but common sense might suggest that the treatment does not make enough of a difference to justify its use or to be practical. Yes, it is possible for a study to have statistical significance, but not practical significance. 5. Yes, there does appear to be a potential to create a bias. 7. No, there does not appear to be a potential to create a bias. 9. The sample is a voluntary response sample and has strong potential to be flawed. 11. The sampling method appears to be sound. 13. The Ornish weight loss program has statistical significance, because the results are so unlikely (3 chances in 1000) to occur by chance. It does not have practical significance because the amount of lost weight (3.3 lb) is so small. 15. The difference between Mendel’s 25% rate and the result of 26% is not statistically significant. According to Mendel’s theory, 145 of the 580 peas would have yellow pods, but the results consisted of 152 peas with yellow pods. The difference of 7 peas with yellow pods among the 580 offspring does not appear to be statistically significant. The difference does not appear to have practical significance. 17. With 40 out of 41 ballots having the Democrat first, it appears that the result is statistically significant. Because of the great advantage enjoyed by Democrats, the results also have practical significance. 19. There appears to be statistical significance given the large discrepancy between 79.1% and 39%. Because the results are so far from yielding a jury of peers, it appears that the results have practical significance. 21. Yes. Each column of 8 AM and 12 AM temperatures is recorded from the same subject, so each pair is matched. 23. The data can be used to address the issue of whether there is a correlation between body temperatures at 8 AM and at 12 AM. Also, the data can be used to determine whether there are differences between body temperatures at 8 AM and at 12 AM. 25. No. The lemon imports are weights in metric tons and the crash fatality rates are fatalities per 100,000 population, so their differences are meaningless. 27. No. The author of an article for the Journal of Chemical Information and Modeling has no reason to collect or present the data in a way that is biased. 29. It is questionable that the sponsor is the Idaho Potato Commission and the favorite vegetable is potatoes. 31. The correlation, or association, between two variables does not mean that one of the variables is the cause of the other. Correlation does not imply causation. Clearly, sour cream consumption is not directly related in any way to motorcycle fatalities. 33. The correlation, or association, between two variables does not mean that one of the variables is the cause of the other. Correlation does not imply causation. 35. The sample is a voluntary response sample, so there is a good chance that the results do not accurately reflect the larger population. 37. a. 700 adults b. 55% 39. a. 559.2 respondents b. No. Because the result is a count of respondents among the 1165 engaged or married women who were surveyed, the result must be a whole number. c. 559 respondents d. 8% 41. Because a reduction of 100% would eliminate all of the size, it is not possible to reduce the size by 100% or more. 43. Because a reduction of 100% would eliminate all plaque, it is not possible to reduce it by more than 100%. 45. If one subgroup receives a 4% raise and another subgroup receives a 4% raise, the combined group will receive a 4% raise, not an 8% raise. The percentages should not be added in this case. 47. All percentages of success should be multiples of 5. The given percentages cannot be correct. Section 1-2 1. The population consists of all adults in the United States, and the sample is the 1001 adults who were surveyed. Because the value of 69% refers to the sample, it is a statistic. 3. Only part (b) describes discrete data. 5. Statistic 7. Parameter 9. Statistic 11. Parameter 13. Continuous 15. Discrete 17. Continuous 19. Discrete 21. Nominal 23. Ordinal 25. Interval 27. Ratio 29. The numbers are not counts or measures of anything. They are at the nominal level of measurement, and it makes no sense to compute the average (mean) of them. 31. The temperatures are at the interval level of measurement. Because there is no natural starting point with 0°F representing “no heat,” ratios such as “twice” make no sense, so it is wrong to say that it is twice as warm in Paris as it is in Anchorage. 33. a. Continuous, because the number of possible values is infinite and not countable b. Discrete, because the number of possible values is finite c. Discrete, because the number of possible values is finite d. Discrete, because the number of possible values is infinite and countable Section 1-3 1. The study is an experiment because subjects were given treatments. 3. The group sample sizes are large enough so that the researchers could see the effects of the two treatments, but it would have been better to have larger samples.
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