Re: st: How to test for difference in predicted prob after prvalue

[Richard Williams <Richard.A.Williams.5@ND.edu>]

At 09:55 PM 12/6/2007, Kristin J. Kleinjans wrote:
> Dear Statalist,
> I run 'mlogit' and use 'prvalue' to get predicted probabilities of
> outcomes for individuals with different characteristics (as described in
> Long and Freeses book on regressions for categorical variables). 'prvalue'
> also returns the confidence intervals of the predicted probabilities.
> I would like to test whether the predicted probabilities of a specific
> outcome are different for, let's say, women with the characteristics of
> men and average women. I hope somebody can help me on how to do this?
>
> Thanks a lot and best regards,
> Kristin
See the help for -prvalue-. The -diff- option might give you what you 
want.  Look to see whether 0 falls within the confidence interval for 
the change; if not, the differences are statistically significant.  Example:

. use "http://www.indiana.edu/~jslsoc/stata/spex_data/ordwarm2.dta";
(77 & 89 General Social Survey)

. quietly mlogit  warm yr89 male white age ed prst

. quietly prvalue, x(male=0) delta save

. prvalue, x(male=1) delta diff

mlogit: Change in Predictions for warm

Confidence intervals by delta method

                     Current     Saved    Change   95% CI for Change
  Pr(y=1SD|x):        0.1311    0.0962    0.0350  [ 0.0094,   0.0606]
  Pr(y=2D|x):         0.3952    0.2621    0.1331  [ 0.0935,   0.1726]
  Pr(y=4SA|x):        0.0994    0.2484   -0.1491  [-0.1795,  -0.1186]
  Pr(y=3A|x):         0.3743    0.3933   -0.0190  [-0.0601,   0.0221]

               yr89       male      white        age         ed       prst
Current=  .39860445          1   .8765809  44.935456  12.218055  39.585259
  Saved=  .39860445          0   .8765809  44.935456  12.218055  39.585259
   Diff=          0          1          0          0          0          0



-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
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EMAIL:  Richard.A.Williams.5@ND.Edu
WWW:    http://www.nd.edu/~rwilliam

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