[R] Two-level Poisson model with cross classified random effects

[Shige Song]

Dear All,

I have two-level data with individual as level-1, birth cohort and
community as level-2. All the level-2 covariates are generated from
the level-1 covariates by cross-classifying by cohort and community.

>From what I read, an ordinary three-level model with individual nesed
within birth cohort nested within community, or individual nested
within community nested within birth cohort do not work well, neither
do model with individual nested within community by cohort. The right
way to go is to estimate a two-level model with two separate random
effects: within cohort and within community. The question I want to
ask is: how to do this using lmer?

I tried the following for a simple unconditioal model:

m1 <- lmer(count ~ offset(log(total)) + (1|comm) + (1|cohort), data, poisson)

where "count" is the dependent variable, "total" is the exposure
variable, "comm" is the community ID, and "cohort" is the birth cohort
ID. Will this be suffice? I got really smalle randome intercept
(5.0000e-10 for community and 4.4226e-05 for cohort), which got me a
bit nervous.

Thanks!

Best,
Shige