ou want to know if redesign of the New Whole Foods has significantly increased sales. You sample 25 customers who shop there regularly. You get the amount spent by these customers during the month before and the month after the opening of the new store. You find the following: The sample mean increase in sales for these customers was $15. The standard deviation of the difference was $40. Assume the distribution of customer sales is normal.

Set up hypotheses for this test.

Calculate the p-value and draw conclusions to determine if sales have increased since the new store opened. Use significance level of .01.

Would your conclusion in part b have been different if your significance level had been .05?

Calculate the 95% confidence interval for the difference between the amount spent per month before and after the opening of the new store. Explain what the specific values for your confidence interval mean.