A manager of a small store wanted to discourage shoplifters by putting signs around the store saying: "Shoplifting is a crime!" However, he wanted to make sure that this sign would not influence customers to buy nothing or to buy less.To test his research hypothesis that customers would actually buy more), he displayed the signs every other Wednesday for 8 weeks, for a total of 4 days displayed.He recorded the store's sales for those four Wednesdays, and then recorded the store's sales for the four alternate Wednesdays, when the signs were not displayed.On the Wednesdays with the sign, the sales were 83, 73, 81, and 79.On the Wednesdays without the sign, sales were 84, 90, 82, and 84.Do these results suggest that the general population of customers buy more when the signs are displayed? Use the .05 significance level.

a) Use the four steps of hypothesis testing

b) Illustrate the distributions involved

c) Calculate the effect size of this study (can use Cohen's d or r)