[R-sig-ME] glmmTMB: dispformula for mixed beta regression

[Timothy MacKenzie]

Dear All,

I have a mixed beta-regression model whose residuals don't spread
evenly across its fitted values unless I add X1 and X2 (two numeric
predictors) to the "dispformula" argument (see below).

Based on the Dispersion model results below, can I say the higher the
value of X2 (0.147987), the more spread-out the residuals but not so
much so for X1 (0.003548)?

In other words, can I think of the variables in dispformula as
"variance covariates"?

glmmTMB(y ~ X1 + X2 + (1 | id), family = beta_family("logit"),
dispformula = ~ X1 + X2)

Dispersion model:
   (Intercept)           X1                   X2
      0.752923        0.003548        0.147987

Thanks,
Tim M