Suppose a company that sells residential carpet cleaning equipment wants to judge the sales effectiveness of two factors: factor A, the type of sales presentation used by its salespeople, and factor B, the type of previous experience or training its salespeople have had in selling this type of equipment. Specifically, there are two types of presentations the company wishes to test. These two levels of factor A are the “hard-sell’” approach, level 1, and the more relaxed “soft-sell” approach, level 2. The company also differentiates among four levels of past experience/training. These levels of factor B are labeled 1 through 4 and are defined as follows: (1) no past experience as a salesperson and no formal training in how to be a salesperson, (2) no past experience and some formal training, (3) some past experience and no formal training, and (4) some past experience and some formal training. To see how presentation and experience/training affect sales, the company runs an experiment with 80 of its recently hired salespeople, 20 of whom fall into each of the four experience/training levels described above. Within each group of 20 salespeople at a given experience/training level, 10 are told to use a hard-sell approach and the other 10 are told to use a soft-sell approach. Of course, the hard-sellers and soft-sellers are instructed very carefully in the types of presentation they are supposed to use. During a 4-month period, the number of sales for each of the 80 salespeople is recorded. The data are provided in the file P12_25.XLS. The company wishes to infer from these data whether the different presentations and experience/training backgrounds cause significant differences in sales.

a. Assess the main effect of the presentation approach factor upon sales.

b. Assess the main effect of the previous experience and training factor upon sales. 

c. Do you find evidence of significant interactions between the two factors in this case? Explain.