Confidence intervals in lmer

U could try the predict function with se.fit=true. I believe this
should give u the predicted score and se and u can calculate CI from
there.

U'll have to create an input matrix with the score u want to predict for.

Chris Howden

On 27/09/2011, at 23:23, Adam Hayward <a.hayward at ...> wrote:

Dear list members,

I have a significant interaction between two continuous variables (it
happens to be a mixed model in lmer, but I imagine the same is applicable to
a glm). The interaction tells me that the relationship between z and y
changes as a function of x, but I want to know whether y has a significant
effect on z at a given value of x. For instance, the interaction might show
that the relationship between body weight and fitness changes with age, but
I want to know if the association between body weight and fitness is
significantly positive at the age of 1. Therefore, I'd like to estimate 95%
CIs or SEs around the association between body weight and fitness at a given
age, but have yet to work out how to do it. Any suggestions would be greatly
appreciated.

Best wishes,
Adam