library(mlmRev)
options(show.signif.stars = FALSE)
(fm1 <- lmer(math ~ year + (1|childid) + (1|schoolid), egsingle))
(fm2 <- lmer(math ~ year + (1|childid) + (year|schoolid), egsingle))
(fm3 <- lmer(math ~ year + (year|childid) + (1|schoolid), egsingle))
(fm4 <- lmer(math ~ year+(year|childid)+(year|schoolid), egsingle))
q("no")