An International Journal of Research (March 2010) study of the influence of reality TV shows on one’s desire to undergo cosmetic surgery, Exercise 12.23 (p. 631). Recall that psychologists modeled desire to have cosmetic surgery (y) as a function of gender (x1), self-esteem (x2), body satisfaction (x3), and impression of reality TV (x4). For this exercise, consider only the independent variables gender (x1) and impression of reality TV (x4).

a. The research psychologists theorize that the impact of one’s impression of reality TV on level of desire for cosmetic surgery will be greater for females than for males. Does this theory imply that the independent variables x1 and x4 interact, or that there is no interaction? Explain.

b. Fit the interaction model, E(y) = β0 + β1x1 + β2x4 + β3x1x4, to the simulated data saved in the BODYIMAGE file.

c. Use the results, part b, to carry out a test for interaction. Make your conclusion using a = .05.