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

From   "Sebastian E. Wenz" <>
Subject   Re: st: How to test for difference in predicted prob after prvalue
Date   Fri, 07 Dec 2007 00:38:24 -0500

Hi Kristin,

as Richard pointed out: sounds like you are interested in the discrete change effect(s) in the probabilities for "sex" (or whatever the name of your variable is, e.g. "male" to stick with Richard's example).

You might want to look (again) at page 249 in Long/Freese (2006 [2nd edition], section 6.6.3). They describe exactly what Richard showed in his example just for race instead of sex (using options -save- and -diff- to calculate the discrete change effect).

Note the option -rest()- which allows you to specify different values for your independent variables. Note further that you will end up with different results (different magnitude) for the discrete change when calculating it at different values of your covariates.

Say hi to good old Europe for me,
Sebastian (@IU Bloomington)

Richard Williams schrieb:

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,
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 "";
(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
HOME: (574)289-5227
EMAIL: Richard.A.Williams.5@ND.Edu

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