From karel.zvara at mff.cuni.cz  Mon Apr  5 14:13:00 2004
From: karel.zvara at mff.cuni.cz (karel.zvara@mff.cuni.cz)
Date: Mon Apr  5 14:13:08 2004
Subject: [Rd] fligner.test (ctest) (PR#6739)
Message-ID: <20040405121300.6693A1046B@slim.kubism.ku.dk>

Full_Name: Karel Zvara
Version: 1.8.1
OS: MS Winows 2000
Submission from: (NULL) (195.113.30.163)


The test statistics of the fligner.test (ctest package) depends on the order of
cases:

> fligner.test(count~spray,data=InsectSprays)

        Fligner-Killeen test for homogeneity of variances

data:  count by spray 
Fligner-Killeen:med chi-squared = 14.4828, df = 5, p-value =
0.01282

> fligner.test(count~spray,data=InsectSprays[order(InsectSprays$count),])

        Fligner-Killeen test for homogeneity of variances

data:  count by spray 
Fligner-Killeen:med chi-squared = 5.4527, df = 5, p-value =
0.3632

> fligner.test(count~spray,data=InsectSprays[order(sample(72)),])

        Fligner-Killeen test for homogeneity of variances

data:  count by spray 
Fligner-Killeen:med chi-squared = 2.7349, df = 5, p-value =
0.7408

The problem lies, I think, in the ordering of centered values x:

 x <- unlist(tapply(x, g, function(u) u - median(u)))


[Rd] fligner.test (ctest) (PR#6739)
karel.zvara@mff.cuni.cz