We do not know the population standard deviations, but a
Chapter , Problem 6.132(choose chapter or problem)
We do not know the population standard deviations, but a sample standard deviation s from so large a sample is usually close to s. Use s in place of the unknown s in this exercise. (a) What population do you think the authors of the study want to draw conclusions about? What population are you certain they can draw conclusions about? (b) Give 95% confidence intervals for the mean performance for each type of store. (c) Based on these confidence intervals, are you convinced that consumers think that pharmacies offer higher performance than the other types of stores? (In Chapter 12, we will study a statistical method for comparing the means of several groups.)
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