I was solving a prep Econometrics exam, with STATA output provided on two different models. They asked me to " Estimate the marginal effect of ability (x variable) on wage (y variable) for the models of output A and B for average levels of wage and ability." Model A is a log-log model for the given x and model B is log-linear model. The answers they provided are Model A: ∂wage/ ∂asvabc = 0.403*(wage/asvabc), at averages we get 0.153. ; Model B: ∂wage/ ∂asvabc = 0.008*wage, at average we get 0.169
Irrespective of the numbers, I don't understand how they know whether to multiply the marginal effect by x or x/y or... Can someone help me with the logic? Or if you know the rule for this?