solution

 

You will have complete sales information for last month in a week, but right now you have data from a random sample of 40 stores. The meanchange in sales in the sample is −3.2%, and the standard deviation of the changes is

12%. Are average sales for all stores different from last month?

(a) State appropriate null and alternative hypotheses. Explain how you decided between the one- and two-sided alternatives.

(b) Find the t statistic and its P-value. State your conclusion using the α = 0.05 significance level.

(c) If the test gives strong evidence against the null hypothesis, would you conclude that monthly sales are different in every one of your stores? Explain your answer