car (version 1.2-16)

levene.test: Levene's Test

Description

Computes Levene's test for homeogeneity of variance across groups.

Usage

levene.test(y, ...)
## S3 method for class 'formula':
levene.test(y, ...)
## S3 method for class 'lm':
levene.test(y, ...)
## S3 method for class 'default':
levene.test(y, group, ...)

Arguments

y

response variable for the default method, or lm or formula object. If y is a linear-model object or a formula, the variables on the right-hand-side of the model must all be factors and must be completely cr

group

factor defining groups.

...

arguments to be passed down, e.g., data for the formula and lm methods.

Value

• returns an object meant to be printed showing the results of the test.

Details

The version of Levene's test implemented here is based on absolute deviations from the group medians. Other, less robust, versions, not implemented, are based on absolute deviations from group means or trimmed means.

References

Fox, J. (1997) Applied Regression, Linear Models, and Related Methods. Sage.

Examples

with(Moore, levene.test(conformity, fcategory))
## Levene's Test for Homogeneity of Variance
##       Df F value Pr(>F)
## group  2   0.046 0.9551
##       42  

with(Moore, levene.test(conformity, interaction(fcategory, partner.status)))
## Levene's Test for Homogeneity of Variance
##       Df F value Pr(>F)
## group  5  1.4694 0.2219
##       39 

levene.test(conformity ~ fcategory*partner.status, data=Moore)
levene.test(lm(conformity ~ fcategory*partner.status, data=Moore))