lme4 (version 0.999999-2)

sleepstudy_PB: Stored parametric bootstrap samples for the sleepstudy data

Description

Parametric bootstrap distribution computed from models fitted to the sleepstudy data set

Usage

sleepstudy_PB

format

Contains a vector of 500 computed deviances under the (simulated) null hypothesis

See Also

simulate-mer for examples of what to do with the parametric boostrap results

Examples

fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy)
fm2 <- lmer(Reaction ~ Days + (1|Subject) + (0+Days|Subject), sleepstudy)

## generic parametric bootstrapping function; return a single simulated deviance
##  difference between full (`m1') and reduced (`m0') models under the
##  null hypothesis that the reduced model is the true model
pboot <- function(m0,m1) {
  s <- simulate(m0)
  L0 <- logLik(refit(m0,s))
  L1 <- logLik(refit(m1,s))
  2*(L1-L0)
}

obsdev <- c(2*(logLik(fm1)-logLik(fm2)))
## parametric bootstrap test of significance of correlation between
##   random effects of `(Intercept)` and Days
## Timing: approx. 70 secs on a 2.66 GHz Intel Core Duo laptop
set.seed(1001)
sleepstudy_PB <- replicate(500,pboot(fm2,fm1))