ScPoEcon / ScPoEconometrics

Undergraduate textbook for Econometrics with R
https://ScPoEcon.github.io/ScPoEconometrics/
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interactions ch 4 #135

Closed floswald closed 4 years ago

floswald commented 5 years ago

in 4.4, interactions, it's confusing that the partila effect of avginc is negative. there should be another model

lm_inter = lm(formula = testscr ~ str + avginc + str*avginc, data = Caschool)
u = update(lm_inter, .~.-avginc)

which removes the avginc effect. how to intuitively explain this?