Re: [R] Syntax of Levene's test

From: Paul Smith <phhs80_at_gmail.com>
Date: Thu 03 Aug 2006 - 08:01:46 EST

On 8/2/06, John Fox <jfox@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
> 39
> > levels(interaction(fcategory, partner.status))
> [1] "high.high" "low.high" "medium.high" "high.low" "low.low"
> [6] "medium.low"
> > levels(fcategory)
> [1] "high" "low" "medium"
> > levels(partner.status)
> [1] "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 ***

      864

tell us that the hypothesis that the variances are equal is (highly) significant?

Paul



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