Compute confidence intervals on the parameters of a *lmer()
model fit (of class"merMod"
).
1 2 3 4 5 6 7 
object 
a fitted [ng]lmer model 
parm 
parameters for which intervals are sought. Specified by an
integer vector of positions, 
level 
confidence level < 1, typically above 0.90. 
method 
a 
zeta 
(for 
nsim 
number of simulations for parametric bootstrap intervals. 
FUN 
bootstrap function; if 
boot.type 
bootstrap confidence interval type, as described
in 
quiet 
(logical) suppress messages about computationally intensive profiling? 
oldNames 
(logical) use oldstyle names for variancecovariance
parameters, e.g. 
... 
additional parameters to be passed to

Depending on the method
specified, confint()
computes
confidence intervals by
"profile"
:computing a likelihood profile and finding the appropriate cutoffs based on the likelihood ratio test;
"Wald"
:approximating
the confidence intervals (of fixedeffect parameters
only; all variancecovariance parameters
CIs will be returned as NA
)
based on the estimated local curvature of the
likelihood surface;
"boot"
:performing parametric
bootstrapping with confidence intervals computed from the
bootstrap distribution according to boot.type
(see
bootMer
, boot.ci
).
a numeric table (matrix
with column and row names) of
confidence intervals; the confidence intervals are computed on the
standard deviation scale.
The default method "profile"
amounts to
1 2 
where the profile
method profile.merMod
does almost all the computations. Therefore it is typically
advisable to store the profile(.) result, say
in pp
, and then use confint(pp, level=*)
e.g., for
different levels.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15  fm1 < lmer(Reaction ~ Days + (DaysSubject), sleepstudy)
fm1W < confint(fm1, method="Wald")# very fast, but ....
fm1W
testLevel < if (nzchar(s < Sys.getenv("LME4_TEST_LEVEL"))) as.numeric(s) else 1
if(interactive()  testLevel >= 3) {
## ~20 seconds, MacBook Pro laptop
system.time(fm1P < confint(fm1, method="profile", ## default
oldNames = FALSE))
## ~ 40 seconds
system.time(fm1B < confint(fm1,method="boot",
.progress="txt", PBargs=list(style=3)))
} else
load(system.file("testdata","confint_ex.rda",package="lme4"))
fm1P
fm1B

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