Perform Levene's test for equality of variances

Tests equality of variances across groups using residuals from a linear model.

Usage

performLeveneTest(model, data, group)

Details

Absolute deviations from group means are analyzed via a one-way ANOVA. The resulting \(F\) statistic has \(k-1\) and \(N-k\) degrees of freedom under the null of equal variances.

Arguments

model

an object of class lm.

data

data frame used to fit model.

group

name of the grouping variable.

Value

An object of class htest containing the F statistic, p-value and degrees of freedom.

References

Levene, H. (1960). Robust tests for equality of variances. In Contributions to Probability and Statistics (pp. 278–292). Stanford University Press.

Brown, M. B., & Forsythe, A. B. (1974). Robust tests for the equality of variances. Journal of the American Statistical Association, 69(346), 364–367. doi:10.1080/01621459.1974.10482955

Examples

 data(mtcars)
 mtcars$cyl <- factor(mtcars$cyl)
 m <- lm(mpg ~ wt, data = mtcars)
 performLeveneTest(m, mtcars, "cyl")
#> 
#> 	Levene's test for equality of variances
#> 
#> data:  mpg ~ wt
#> F = 2.6597, df1 = 2, df2 = 29, p-value = 0.08699
#>