Imagine two studies of a diet pill that, manufacturers claim, will make people lose weight. The first study is based on a random sample of 100 men and women who had been taking the diet pill for 12 months. A hypothesis test is carried out to determine whether their mean weight change is negative. The second study was based on a random sample consisting solely of 100 men (no women) who had been taking the weight-loss pill for 12 months. The same hypothesis test is carried out to deter mine whether their mean weight change is negative. Which study's hypothesis test will have greater power to detect whether the mean weight change is truly less than 0? Assume that the diet pill really does lower weight and that the effect of weight loss is larger on men than on women.
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