# Re: st: Calculate Marginal Effect after IVPROBIT

 From "Austin Nichols" To statalist@hsphsun2.harvard.edu Subject Re: st: Calculate Marginal Effect after IVPROBIT Date Mon, 9 Jul 2007 11:01:30 -0400

```Prabal Kumar De <prabal.de@nyu.edu>:
See
http://www.stata.com/support/faqs/stat/mfx_nose.html
and note -dprobit- uses these formulas to calculate marg fx and SEs:

Indicator Variables
Dp = F(x2*b) - F(x1*b)
d(Dp)/db = f(x2*b)*x2 - f(x1*b)*x1
Vhat(Dp) = [d(Dp)/db)]' Vhat(b) [d(Dp)/db]
Continuous Variables
p = F(x*b)
dp/dx = f(x*b)*b = g(b)
dg/db = f'(x*b)b'x + f(x*b)I
Vhat(dp/dx) = [dg/db] Vhat(b) [dg/db]'

presumably you could do this "by hand" as well.

On 7/8/07, Prabal Kumar De <prabal.de@nyu.edu> wrote:
```
```Hi!
I need to know what is the best way to calculate the marginal effect after running IVPROBIT. I use -mfx- , but it is not reporting standard errors ( even after specifying the value at which to be calculated). I could not find something like -divprobit-
Any help will be much appreciated.
```
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