Re: [S] distribution-free tests for dispersion

Anthony Rossini (
26 Mar 1998 10:03:57 -0500

>>>>> S Raessler <> writes:

>does anyone have some S-Plus-functions of test statistics which could
>be used, when the assumption of normal distribution is invalid and a
>test of identical variances shall be performed. Unfortunately our
>distributions observed are well skewed to the right. Thus we are
>searching for tests for dispersion in the two-sample case such like
>the Siegel-Tukey, Mood, Ansary-Bradley, Moses or similar ones.

They are not too hard to write up. See some of the (incomplete)
implementation somewhere under

also, on the same machine, is the ctest package, in the R archive
CRAN, which ought to work (maybe with small modifications) under S.
Start at
and look for the CRAN packages (somewhere in CRAN).


Anthony Rossini
Manifold Graphics / Epimetrics

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