28. Sales performance. A chain that specializes in healthy and organic food would like to compare the sales performance of two of its primary stores in the state of Massachusetts. These stores are both in urban, residential areas with similar demographics. A comparison of the weekly sales randomly sampled over a period of nearly two years for these two stores yields the following information:

a) Create a 95% confidence interval for the difference in the mean store weekly sales.

b) Interpret your interval in context.

c) Does it appear that one store sells more on average than the other store?

d) What is the margin of error for this interval?

e) Would you expect a 99% confidence interval to be wider or narrower? Explain.

f) If you computed a 99% confidence interval, would your conclusion in part c change? Explain.

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Store N Mean StDev Minimum Median Maximum Store #1 9 242170 23937 211225 232901 292381 Store #2 9 235338 29690 187475 232070 287838