Check model for (non-)normality of residuals.
Check model for (non-)normality of residuals.
check_normality(x, ...)
## S3 method for class 'merMod'
check_normality(x, effects = c("fixed", "random"), ...)x |
A model object. |
... |
Currently not used. |
effects |
Should normality for residuals ( |
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.
Invisibly returns the p-value of the test statistics. A p-value < 0.05 indicates a significant deviation from normal distribution
For mixed models, studentized residuals are used for the test,
not the standardized residuals. There is also a
plot()-method
implemented in the
see-package.
m <- lm(mpg ~ wt + cyl + gear + disp, data = mtcars)
check_normality(m)
# plot results
if (require("see")) {
x <- check_normality(m)
plot(x)
}
## Not run:
# QQ-plot
plot(check_normality(m), type = "qq")
# PP-plot
plot(check_normality(m), type = "pp")
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.