Levene_test: Levene's Test of Homogeneity of Variances
In varequal: Tests and Measures for Homoscedasticity

Levene_test

R Documentation

Levene's Test of Homogeneity of Variances

Description

Performs Levene's test to assess the null hypothesis that the variances are equal across all groups (samples) defined by the independent variable.

Usage

Levene_test(
  data,
  formula,
  alpha = 0.05,
  silent = FALSE,
  summary = FALSE,
  misc = FALSE,
  transform = function(x) abs(x - stats::median(x))
)

Arguments

`data`	A data frame containing the variables specified in the formula.
`formula`	A formula of the form `DV ~ IV`, where `DV` is the dependent (response) variable and `IV` is the independent (grouping) variable.
`alpha`	A numeric value specifying the significance level. Must be between 0 and 1. Default is 0.05.
`silent`	A logical value. If `FALSE` (default), results are printed to the console. If `TRUE`, no output is printed.
`summary`	A logical value (default: `FALSE`). If `TRUE`, a summary table for the input data is returned.
`misc`	A logical value. If `FALSE` (default), only essential parameters are returned. If `TRUE`, additional auxiliary parameters are included in the output.
`transform`	A function used to transform the response variable into deviations from a specified location measure.

Details

transform: The concept is similar to ANOVA procedure (transform the response variable to residuals before analysis). Possible transformation are:

y' = |yi - ybar| (default)
y' = (yi - ybar) ^ 2
y' = ln((yi - ybar) ^ 2)
y' = sqrt(|yi - ybar|)

The ybar could be either mean, median (default), or trimmed-mean.

Value

A list containing the test statistics, p-value, degrees of freedom, and optionally a summary table and/or auxiliary parameters, depending on the values of summary and misc.

References

Levene, H. (1960). Robust tests for equality of variances. In I. Olkin (Ed.), Contributions to probability and statistics: Essays in honor of Harold Hotelling (pp. 278–292). Stanford University Press.

Sharma, D., & Kibria, B. M. G. (2013). On some test statistics for testing homogeneity of variances: A comparative study. Journal of Statistical Computation and Simulation, 83, 1944–1963. https://doi.org/10.1080/00949655.2012.675336

Zhou, Y., Zhu, Y., & Wong, W. K. (2023). Statistical tests for homogeneity of variance for clinical trials and recommendations. Contemporary Clinical Trials Communications, 33, 101119. https://doi.org/10.1016/j.conctc.2023.101119

Examples

df0 <- roGFP[[1]]
out <- Levene_test(df0, ro ~ grp)
boxplot(ro ~ grp, df0, horizontal = TRUE)
points(x = df0$ro, y = jitter(as.numeric(df0$grp), amount = 0.15))

varequal documentation built on Sept. 5, 2026, 5:08 p.m.