Levene's test output

I don't really get the output of the performed Levene's test.

One answer would be to read John Fox's rather good book, for which car is the corresponding R package.

Another is to look up leven'es test; a reasonably authoritative web reference for the calculation is http://www.itl.nist.gov/div898/handbook/eda/section3/eda35a.htm
if you followed that, you would find that 356 turns up somewhere important ...

A clue: It is unlikely to be coincidence that you have 358 data points in 2 groups.... and that the 356 turns up in the column headed "Df" in the leveneTest output.


S Ellison

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Dear pieter,

On Fri, 21 Jun 2013 10:12:26 +0200

Hey,
I don't really get the output of the performed Levene's test.
So in short.
two data sets, one with 75 elements, one with 283.
And I want to check whether they have the same variance.

I did a LeveneTest
And this is the output:

Levene's Test for Homogeneity of Variance (center = median)
        Df F value   Pr(>F)
group   1  10.948 0.001033 **
       356
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

So I would think that H0 is being rejected? for everything except 99.9%?

0.001033 is the p-value for the null hypothesis of equal variances.

But what does the 356 mean?

The residual df for the test.

Is this test performed correctly? 

I certainly hope so.

John

------------------------------------------------
John Fox
Sen. William McMaster Prof. of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox/

group is a vector with 1's and 2's 
appointing the two datasets...



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