Re: st: Marginal Effects

[Andreas Kuhn <akuhn@access.unizh.ch>]

peter harper wrote:

> Dear Statalist
> I am trying to do marginal effects after oprobit. 
> I have run a oprobit regression on a dependent
> variable, which is called price3. Its other
> categories
> are price2 and price1, which obviously I have not
> used. So after I have run
> . oprobit price3 x1  x2 x3 
> I issued the command
> . mfx compute, predict(outcome(3))
> the message I got was put a value of price3 or
> #1,#2...
> or worde to that effect
> so I tried
> . mfx compute, predict(outcome(#3))
> the message I then got was there is no category 3,
> there are only 2 categories.
> I suspect, this is because this price3 itself is
> categorised under 0 and 1. 0 is people who do not
> think price is important and 1 is for people who
> think
> price is important.
> so I ran a marginal effects using
> .mfx compute, predict (outcome(#2)
> All I should want is M.E. of price3 is it not? as I
> have run the oprobit using that variable. So I ran
> . mfx compute, predict(outcome(#2))
> Is that the right thing to do, as I want the M.E.
> for
> the regression I ran with the dependent variable as
> price3.
> Please confirm, if I am doing it correctly.
> Please let me know if you need further clarification.
> Thanks in advance
>
>
>
>
>
>
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>  
Dear Peter,

You should install the - spost - package (written by Jeremy Freese and 
Scott Long; by the way: they have written a very useful book concerning 
the estimation and the interpretation of the ordered probit model with 
Stata, among others. "Regression Models for Categorial Dependent 
Variables Using Stata", published by Stata Press 2001.), which is 
available for version 7 or 8.
Having installed this package, you can then use the command - prchange - 
for estimating marginal effects of the ordered probit model.

Best regards, Andreas

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