Function lmer_t provides confidence intervals and p-values based on the m-l-1
heuristic, the Satterthwaite and Kenward-Roger methods for models fitted with lmer.
lmer_t(object, method = c("Heuristic", "Satterthwaite", "Kenward-Roger"),
level = 0.95)
an object representing a linear mixed effects model, as returned by lmer
a character string that selects the method used to determine the degrees of freedom.
a number between 0 and 1, the level of the confidence intervals
The function returns a list with two elements "lmer" - the original object - and
"coefTab" which is a matrix with estimates, standard errors, t-statistics, degrees of
freedom, lower and upper confidence intervals, and p-values.