performance (version 0.9.2)

check_normality: Check model for (non-)normality of residuals.

Description

Check model for (non-)normality of residuals.

Usage

check_normality(x, ...)
# S3 method for merMod
check_normality(x, effects = c("fixed", "random"), ...)

Value

The p-value of the test statistics. A p-value < 0.05 indicates a significant deviation from normal distribution.

Arguments

x

A model object.

...

Currently not used.

effects

Should normality for residuals ("fixed") or random effects ("random") be tested? Only applies to mixed-effects models. May be abbreviated.

Details

check_normality() calls stats::shapiro.test and checks the standardized residuals (or Studentized residuals for mixed models) for normal distribution. Note that this formal test almost always yields significant results for the distribution of residuals and visual inspection (e.g. Q-Q plots) are preferable.

Examples

m <<- lm(mpg ~ wt + cyl + gear + disp, data = mtcars)
check_normality(m)

# plot results
if (require("see")) {
  x <- check_normality(m)
  plot(x)
}
if (FALSE) {
# QQ-plot
plot(check_normality(m), type = "qq")

# PP-plot
plot(check_normality(m), type = "pp")
}