[R] Syntax of Levene's test
phhs80 at gmail.com
Thu Aug 3 00:01:46 CEST 2006
On 8/2/06, John Fox <jfox at mcmaster.ca> wrote:
> The argument y is the response variable and group is a factor defining
> groups (as ?levene.test says). If you have more than one factor, then you
> can use interaction() to create from them a factor with levels given by the
> product set of the levels of the individual factors. Here's an example
> > library(car)
> > data(Moore)
> > attach(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
> > levels(interaction(fcategory, partner.status))
>  "high.high" "low.high" "medium.high" "high.low" "low.low"
>  "medium.low"
> > levels(fcategory)
>  "high" "low" "medium"
> > levels(partner.status)
>  "high" "low"
> I'll add a couple of examples to the help page.
Thanks, John. Now, I understand how to use levene.test. There is only
a question remaining: is the null hypothesis corresponding to
homogeneity of variances, i.e., should one conclude that
Levene's Test for Homogeneity of Variance
Df F value Pr(>F)
group 95 3.5919 < 2.2e-16 ***
tell us that the hypothesis that the variances are equal is (highly)
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