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Dispersion Measures

To: s-news@lists.biostat.wustl.edu
Subject: Dispersion Measures
From: Paul.Reynolds@ILIM.COM
Date: Mon, 24 Oct 2005 10:00:09 +0100
Dear Fellow S+ Users,

Background: I have monthly time series data for a metric over a 15 year
period with variable numbers of monthly observations.  I wish to analyse the
spread in these metric values over time but am wary of using a simple
'standard deviation'...  

Question: Can anyone please advise of alternative robust measures of
dispersion for a noisy data set with outliers (rather than the default
'standard deviation').  For example, inter-quartile ranges may be a
possibility, but if anyone can advise of other measures that may be of
interest I would be grateful.   [I appreciate that the use of some methods
may be dependent on data size: the number of observations at any given time
point may vary from small sample (5 or less) - for which meaningful
statistics may not be possible - up to about 100].

Thanks and kind regards
Paul
[Windows User, S+ 6.2 Professional]


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