[R] levene.test

[Peter Ehlers]

On 2010-07-14 6:47, martanair wrote:
>
> the value of the F-test is uncorrect.
> If I calculate the Levene's Test for Homogeneity of Variance with SPSS I get
> F = 5.128 Pr (>  F) = 0.033
> Why?

Why do you assume that SPSS provides the "correct" value?

> what is the exact formula which R calculate Levene's test for two groups?

John Fox has explained the formula used in pkg:car.
You can also have a look at Wikipedia (see "Brown-Forsythe test").

Finally, this won't be necessary with John's new version of car,
but pkg:lawstat has a levene.test() function that lets you
select the statistic to center your groups on. SPSS uses the
mean, car uses the median.

   -Peter Ehlers