468 CHAPTER 9 Inferences from Two Samples a. Use a 0.01 significance level to test the claim that cars in two queues have a mean waiting time equal to that of cars in a single queue. b. Construct the confidence interval suitable for testing the claim in part (a). Two Lines 64216 86340200630333329915553 5978651090663518566268350 95100 163 101 One Line 64 157 142 279 253 476 478 474 402 722 761 692 837 903 734 606 268 310 129 133 122 129 233 461 482 518 509 580 19. Regular Coke and Diet Coke Listed below are weights (lb) of samples of the contents of cans of regular Coke and Diet Coke (from Data Set 37 “Cola Weights and Volumes” in Appendix B). a. Use a 0.01 significance level to test the claim that the contents of cans of regular Coke have weights with a mean that is greater than the mean for Diet Coke. b. Construct the confidence interval appropriate for the hypothesis test in part (a). c. Can you explain why cans of regular Coke would weigh more than cans of Diet Coke? Regular 0.8192 0.8150 0.8163 0.8211 0.8181 0.8247 0.8062 0.8128 0.8172 0.8110 0.8251 0.8264 Diet 0.7773 0.7758 0.7896 0.7868 0.7844 0.7861 0.7806 0.7830 0.7852 0.7879 0.7881 0.7826 0.7923 0.7852 0.7872 0.7813 20. Blanking Out on Tests Many students have had the unpleasant experience of panicking on a test because the first question was exceptionally difficult. The arrangement of test items was studied for its effect on anxiety. The following scores are measures of “debilitating test anxiety,” which most of us call panic or blanking out (based on data from “Item Arrangement, Cognitive Entry Characteristics, Sex and Test Anxiety as Predictors of Achievement in Examination Performance,” by Klimko, Journal of Experimental Education, Vol. 52, No. 4.) Is there sufficient evidence to support the claim that the two populations of scores have different means? Is there sufficient evidence to support the claim that the arrangement of the test items has an effect on the score? Is the conclusion affected by whether the significance level is 0.05 or 0.01? Questions Arranged from Easy to Difficult 24.64 39.29 16.32 32.83 28.02 33.31 20.60 21.13 26.69 28.90 26.4324.23 7.1032.8621.06 28.89 28.71 31.73 30.02 21.96 25.49 38.81 27.85 30.29 30.72 Questions Arranged from Difficult to Easy 33.62 34.02 26.63 30.26 35.91 26.68 29.49 35.32 27.24 32.34 29.34 33.53 27.62 42.91 30.20 32.54 Larger Data Sets. In Exercises 21–24, use the indicated Data Sets in Appendix B. The complete data sets can be found at www.TriolaStats.com. Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. 21. Are We Getting Heavier? Exercise 17 used weights of small samples of males from Data Set 2 “ANSUR I 1988” and from Data Set 3 “ANSUR II 2012.” Repeat Exercise 17 using the 1774 weights of males from the ANSUR I 1988 data set and the 4082 weights of males from the ANSUR II 2012 data set.
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