Date: Mon, 31 Jan 2005 22:01:35 -0500
Reply-To: Richard Ristow <firstname.lastname@example.org>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Richard Ristow <email@example.com>
Subject: Effect-size measure in crosstab
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It's shameful not to know this after being around so long, but what are
recommended effect-size measures for categorical-by-categorical
comparisons - "crosstabs"?
I've got some where the significance by chi-square p<.001; but the
sample size is large, and, at least by eye, the effect is not
I've thought of using reduction in Shannon entropy -- i.e., Shannon
information -- as a measure.(1) It is sample-size independent, and
tests pretty much what chi-square tests: that knowing one of the
variables, tells you anything about the other. I don't think it's a
symmetric measure. And if it's included in the symmetric or asymmetric
statistics available with SPSS Crosstabs, I don't recognize it.
Advice much appreciated!
(1) If there are k possible events and even i occurs with probability
Shannon entropy = -sum(i=1 to k) p(i)log2(p(i)).