Could you post the commands you ran?

Tom

On Wed, May 25, 2011 at 12:25 PM, Yuqing Ren <chingren@umn.edu> wrote:

> Dear All,
>
> I have a quick questions about comparing results from lmer and from
> glm. We are running analysis to predict a person's likelihood of
> leaving a project with some people affiliated with multiple projects
> (binary outcome and crossed random effects).
>
> The data consist of three levels: projects, members (crossed with
> projects with 70% members with one project and 30% with multiple
> projects), and time series nested within individuals. I ran the
> analysis with first glm (family=binomial) and then lmer
> (family-binomial and + (1 | projectid) + (1 | memberid) to account for
> the random effects). The two analyses have the same covariates:
> project size and scope and some individual member attributes such as
> tenure and past performance.
>
> Theoretically, I expect the coefficients to be similar between the two
> results with some differences in the significance test or confidence
> intervals. However, I found three coefficients flipped signs between
> the two, which is very puzzling. I ran another set of analysis with a
> continuous dependent variable (quantity of work completed) and found
> similar coefficients between the two (results from lm and lmer).
>
> So my question is: should we expect the results from glm and lmer to
> be similar? If we should see different results, is it because of the
> distribution being binomial rather than normal or other reasons? Which
> set of results is more reliable and should be included in our paper?
>
> Thanks very much.
>
> Ching Ren
>
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