* R. Carter Hill, William E. Griffiths and Guay C. Lim, * Principles of Econometrics, Fourth Edition, Wiley, 2011. * Chapters 5.7 - Interaction Variables READ (pizza4.dat) / names * Summary statistics STAT / ALL OLS pizza age income * Add an interaction variable (p. 196) GENR age_inc = age*income OLS pizza age income age_inc * The TEST command uses the results from the previous OLS * estimation command. On the TEST command the variable names * represent the regression coefficients. * Estimate marginal effects (bottom of p. 196) * On the TEST command output the marginal effect is reported as * TEST VALUE. A standard error is also reported. * INCOME = $25,000 TEST age + age_inc*25 * INCOME = $90,000 TEST age + age_inc*90 STOP