A large furniture store stations salespeople near its entrance to greet customers ...

A large furniture store stations salespeople near its entrance to greet customers and offer assistance in shopping. The salespeople, who work on a commission basis, tell the customers their name and hand them a business card. A psychologist thinks that the salespersons’ intrusiveness might cause customers to buy less furniture rather than more  furniture. She convinces the store’s management to let her study the issue. Customers are randomly selected to either receive or not receive a salesperson’s offer of assistance immediately on entering the store. The amount of customers’ purchases are then logged as they leave the store. Here are the data: Amount of Purchase, in U.S. Dollars
Immediate Assistance No Assistance Unless Requested
0 761
2,274 0
0 2,592
0 0
0 1,037
362 0
855 84
0 0
0 672
1,273 0

a. What are the independent and dependent variables in this study?
b. State the null hypothesis and the directional (one-tailed) research hypothesis.
c. Calculate t and compare it with the tabled critical t at the .01 and .05 α levels. Can you reject the null hypothesis?