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# The Role of Confidence

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Chapter 21 The Role of Confidence Intervals in Research Copyright 2005 Brooks Cole a division of Thomson Learning Inc Thought Question 1 Compare weight loss over 1 year in men who diet but do not exercise and vice versa Results 95 confidence interval for mean weight loss for men who diet but do not exercise is 13 4 to 18 0 pounds 95 confidence interval for mean weight loss for men who exercise but do not diet is 6 4 to 11 2 pounds a Does this mean 95 of all men who diet will lose between 13 4 and 18 0 pounds Explain b Do you think you can conclude that men who diet without exercising lose more weight on average than men who exercise but do not diet Copyright 2005 Brooks Cole a division of Thomson Learning Inc 2 Thought Question 2 First confidence interval in Question 1 was based on results from 42 men Confidence interval spans a range of almost 5 pounds If the results had been based on a much larger sample do you think the confidence interval for the mean weight loss would have been wider narrower or about the same Explain your reasoning Copyright 2005 Brooks Cole a division of Thomson Learning Inc 3 Thought Question 3 In Question 1 we compared average weight loss for dieting and for exercising by computing separate confidence intervals for the two means and comparing the intervals What would be a more direct value to examine to make the comparison between the mean weight loss for the two methods Copyright 2005 Brooks Cole a division of Thomson Learning Inc 4 Thought Question 4 Case Study 5 3 examined the relationship between baldness and heart attacks Results expressed in terms of relative risk of heart attack for men with severe vertex baldness compared to men with no hair loss 95 confidence interval for relative risk for men under 45 years of age 1 1 to 8 2 a Explain what it means to have a relative risk of 1 1 in this example b Interpret the result given by the confidence interval Copyright 2005 Brooks Cole a division of Thomson Learning Inc 5 21 1 Confidence

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