I am using the glmer() function from the package lme4 for a mixed logistic regression model. Here, the formula is Y ~ X + Z + X:Z, where Y is the binomial outcome, X is a categorical predictor with 3 levels (X1, X2, X3, where X1 is the baseline), and Z is a continuous predictor.

In the summary plot, however, I find effect sizes, standard error and p-values for

intercept

X

Y

X1:Y

X2:Y

X3:Y

I am a little bit confused since the baseline-interaction term appears also in the summary?! In other functions from other packages this is not the case. So how can I interpret these interaction terms in glmer()?

Thanks!