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st: question on -treatreg-

From   "Martin Weiss" <>
To   <>
Subject   st: question on -treatreg-
Date   Tue, 10 Jun 2008 14:47:05 +0200

Dear Statalisters,

I am wondering how one can reconcile the predictions flowing from -treatreg-
with a dependent variable in logs or in levels. See for yourself

webuse labor, clear

	g byte wc = we > 12
	la var wc "Wife attended college (assumed)"
	la def wi 0 "no college" 1 "college"
	la val wc wi

	noi ta wc

*    Obtain full ML estimates with log specification

	noi treatreg ww wa cit, treat(wc=wmed wfed)
	predict logpredpos, yctrt
	predict logpredneg, ycntrt
	*put dependent in levels
	g levelww=exp(ww)
	noi treatreg levelww wa cit, treat(wc=wmed wfed)

	predict levelpredpos, yctrt
	predict levelpredneg, ycntrt

	scatter logpredpos levelpredpos, nodraw name(pos, replace)
	scatter logpredneg levelpredneg, nodraw name(neg, replace)

gr combine pos neg, cols(1)

How could one go back from logpredpos to levelpredpos? It is not as simple
as exponentiating the logpredpos, but what do you add to that?

Thanks in advance,
Martin Weiss

Diplom-Kaufmann Martin Weiss
Mohlstrasse 36
Room 415
72074 Tuebingen

Fon: 0049-7071-2978184




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