# st: RE: Marginal Effect Probit - percent points?

 From "Villa Lora, Juan Miguel" To Subject st: RE: Marginal Effect Probit - percent points? Date Mon, 31 Aug 2009 10:55:36 -0400

```I guess the interpretation would be as simple as "an unit change in the RHS variable would lead a change in the probability that the endogenous variable in X% ". Remember that this change is calculated on the probability average since you get a vector of dF/dX, which implies a % change of the cumulative density function.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sophia Rüster
Sent: Lunes, 31 de Agosto de 2009 10:37 a.m.
To: statalist@hsphsun2.harvard.edu
Subject: st: Marginal Effect Probit - percent points?

Dear all,

I have run a Probit model and calculated the marginal effects afterwards.
Assuming a continuous RHS variable, the marginal effect is interpreted the following way: "An infinitesimal change in the RHS variable changes the probability that the endogenous variable takes the value of one by X%".

Are these X% (1) percent points or (2) percent of the actual value?

Example:
Pr(Y=1) = 0.5
Marginal Effect of x on y = 0.1

(1) Does it mean Pr(Y=1) changes to 0.6 (0.5+0.1)
(2) or does it mean Pr(Y=1) changes to 0.55 (0.5*1.1)

Thanks a lot for a brief response!
Sophie

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