[R-lang] Plotting CI from Mixed Effects Model

[David Reitter]

Roger, Corey,

On 30 Sep 2007, at 00:47, Roger Levy wrote:
> So with that explanation, the recommendation I'd give you for what you
> want to do is: rerun lmer four different ways, each time resetting the
> contrasts for place and voice such that you cover the four logical
> possibilities, and report the CI for each cell on the basis of the CIs
> (either classical or HPD) obtained when that cell is the default.

Do you see a problem with explicitly getting the model to estimate  
the constrasts for all the factor combinations without parameters for  
the main effects an the intercept, using

model <- glmmPQL(data=d, fixed=c ~ (a*b) - a - b - 1, random=...,  
family=...)
(This is with the MASS / nlme libraries, syntax from the top of my  
head.)

and then using `intervals.lme',

intervals(model, level=0.95)

Would this produce the same results?

> This means that if
> you wanted to construct a simultaneous confidence "interval" on  
> multiple
> parameter of the model, it would actually be a confidence *region* in
> the form of an ellipsoid.  The symmetric confidence intervals we  
> look at
> around the point estimate of a single parameter of the model have  
> simply
> marginalized out all the other model parameters.

In the above approach, we would basically only estimate parameters  
for a single factor - which is simply the product of factors a and b,  
e.g. all combinations of their respective levels. That way, there  
shouldn't be interactions between multiple parameters.

- David


--
David Reitter
ICCS/HCRC, Informatics, University of Edinburgh
http://www.david-reitter.com