[R-sig-ME] Random effects in multinomial regression in R?

[Souheyla GHEBGHOUB]

Dear Philip,

I understand , here is the structure of my data in case it could help.

I have 3 groups of participants (control, treatment1, treatment2). Each
group was tested twice, once before treatment (pretest) and once after
treatment (posttest).
In each test, they were tested on knowledge of 28 words, scores are
dichotomous (0 = unknown , 1 = known). Tests are the same.

I calculated change from pretest to posttest :
if pretest 0 and posttest 0 = no gain
if pretest 1 and posttest 1 = no gain
if pretest 0 and posttest 1 = gain
if pretest 1 and posttest 0 = decline
So I ended up with a dependent variable called Change with 3 levels
(no_gain, gain, decline) and I tried to predict it using Group and Pretest
as covariates using multinomial logit model. mod0 <- brm(Change ~ Pretest +
Group) I would like to add random effects for subjects but don't know
what's the best form when Time factor is absent.

I hope other statisticians who read this could help
Thank you
Souheyla

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