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# Confidence intervals for sample; Cohen's guidelines, two-tai

8.22. Calculate the 95% confidence interval for the following fictional data regarding daily TV viewing habits: µ = 4.7; &#963; = 1.3 hours; sample of 78 people with a mean of 4.1 hours.

8.30. For each of the following d values, identify the size of the effect using Cohen's guidelines. (a) d = 0.79 (b) d = - 0.43 (c) d = 0.22 (d) d = -0.04

8.32. For each of the following z statistics, calculate the p value for a two-tailed test. (a) 2.23 (b) -1.82 (c) 0.33

8.34. For each of the three z statistics you considered in number 8.32 as a two-tailed test, determine Prep: (a) 2.23 (b) -1.82 (c) 0.33

8.48. Let's assume the average speed of a serve in women's tennis is around 118 mph with a standard deviation of 12 mph. We recruit 26 amateur tennis players to use our method this time, and after six months we calculate a group mean of 123 mph.
(a) Using a 95% confidence interval, test the hypothesis that our method makes a difference. (b) Compute the effect size and describe its strength.

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