An experiment tested the effects of package design and shelf display on the likelihood of purchase of Special K cereal.

Package design and shelf display were varied at two levels each, resulting in a 2 3 2 design. Purchase likelihood was measured on a 7-point scale. The results are partially described in the following table.

Source of Variation Sum of Squares df Mean Square F Significance of F v2 Package design 68.76 1 Shelf display 320.19 1 Two-way interaction 55.05 1 Residual error 176.00 40

a. Complete the table by calculating the mean square, F, significance of F, and v2 values.

b. How should the main effects be interpreted?