st: Interpretation of -mfx-

 From "Herve STOLOWY" To Subject st: Interpretation of -mfx- Date Wed, 18 Jun 2008 11:46:40 +0200

```Dear Statalisters:

I run -mfx- after -logit- and have some difficulties to interpret some of the elements displayed in the mfx output. I provide below an example.

. mfx

Marginal effects after logit
y  = Pr(ar_english) (predict)
=   .7000302
------------------------------------------------------------------------------
variable |      dy/dx    Std. Err.     z    P>|z|  [    95% C.I.   ]      X
---------+--------------------------------------------------------------------
size2 |   .1079549      .00804   13.43   0.000   .092198  .123712    5.5668
int_sa~s |   .2011792      .03358    5.99   0.000   .135357  .267001   .392419
listing*|   .2169588      .03599    6.03   0.000    .14641  .287507   .109184
concent |  -.0028278      .00046   -6.18   0.000  -.003725 -.001931   51.4973
roa_~l_w |  -.4606671      .11855   -3.89   0.000  -.693019 -.228316   .003571
growt~p3 |   .1219913      .02001    6.10   0.000   .082775  .161208   1.38071
levera~f |  -.4810831      .06037   -7.97   0.000  -.599402 -.362765   .570702
tongu~rt |  -.0413828      .00491   -8.42   0.000  -.051014 -.031751   2.36958
ln_mkt~b |  -.0316398      .00991   -3.19   0.001  -.051056 -.012223   26.8543
------------------------------------------------------------------------------
(*) dy/dx is for discrete change of dummy variable from 0 to 1

I understand the meaning of dy/dx, 95% CI and X. However, I don't know how to read the z and associated p-value. What is the underlying test?  Is the Std. Err. an important element to display? In other terms, if you want to present some of the elements of the output in a paper, which ones would you chose? dy/dx? Std. Err? z? p(z)? CI? X?

I checked in the Stata manual but did not find the answer (probably because the answer is too obvious).

Best regards

Herve Stolowy

***********************************************************
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HEC Paris
Departement Comptabilite Controle de gestion / Dept of Accounting and Management Control
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mail: stolowy at hec dot fr
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