summary.lmerModLmerTest function

Summary Method for Linear Mixed Models

Summaries of Linear Mixed Models with coefficient tables including t-tests and p-values using Satterthwaites's or Kenward-Roger's methods for degrees-of-freedom and t-statistics.

## S3 method for class 'lmerModLmerTest'
summary(object, ..., ddf = c("Satterthwaite", "Kenward-Roger", "lme4"))

Arguments

• object: an lmerModLmerTest object.
• ...: additional arguments passed on to lme4::summary.merMod
• ddf: the method for computing the degrees of freedom and t-statistics. ddf="Satterthwaite" (default) uses Satterthwaite's method; ddf="Kenward-Roger" uses Kenward-Roger's method, ddf = "lme4" returns the lme4-summary i.e., using the summary method for lmerMod objects as defined in the lme4-package and ignores the type argument. Partial matching is allowed.

Returns

A summary object with a coefficient table (a matrix) including t-values and p-values. The coefficient table can be extracted with coef(summary(<my-model>)).

Details

The returned object is of class c("summary.lmerModLmerTest", "summary.merMod") utilizing print, coef and other methods defined for summary.merMod objects. The "Kenward-Roger" method use methods from the pbkrtest package internally to compute t-statistics and associated degrees-of-freedom.

Examples

# Fit example model:
data("sleepstudy", package="lme4")
fm <- lmer(Reaction ~ Days + (1|Subject) + (0+Days|Subject), sleepstudy)

# Get model summary:
summary(fm) # Satterthwaite df and t-tests

# Extract coefficient table:
coef(summary(fm))

# Use the Kenward-Roger method
if(requireNamespace("pbkrtest", quietly = TRUE))
  summary(fm, ddf="Kenward-Roger")

# The lme4-summary table:
summary(fm, ddf="lme4") # same as summary(as(fm, "lmerMod"))

See Also

contest1D for one degree-of-freedom contrast tests and KRmodcomp for Kenward-Roger F-tests.

Author(s)

Rune Haubo B. Christensen and Alexandra Kuznetsova