# [R-sig-ME] predicted probabilities lmer

Dimitris Rizopoulos d.rizopoulos at erasmusmc.nl
Wed Jun 15 15:09:31 CEST 2011

Well it depends on what exactly do you mean by 'FIXED part only'. If you
mean the predicted probabilities for the "average" subject (i.e., a
subject with random effect value zero), then you can simply obtain these
probabilities from the estimated coefficients of the model.

However, if you mean the marginal/population probabilities, i.e., the
probabilities averaged over the subjects, then you in fact need,

P(y = 1) = \int P(y = 1 | b) f(b) db,

where f(b) is the normal density for the random effects. One option to
get those is using sampling with a bit of extra programming.

I hope it helps.

Best,
Dimitris

On 6/15/2011 2:47 PM, Ben Pelzer wrote:
> Hi all,
>
> Is there a simple method to obtain the predicted probabilities based on
> the FIXED part only of a random intercept logistic regression model
> using lmer?
> Thanks for any help!
>
> Ben.
>
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--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
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