Hypothesis Testing for Two Independent Means

We wish to test the hypothesis that people exercising regularly sleep more on average than those that don't exercise at all. Here is data on a group of individuals for both groups. The number of hours of sleep for each person is recorded. Assume the population standard deviations are different.

Let μ1\mu_1 represent the mean hours of sleep for people that exercise regularly.
Let μ2\mu_2 represent the mean hours of sleep for people that don't exercise.

a) Find the standard error of x1x2\overline{x}_1-\overline{x}_2
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