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st: -kaplansky- available from SSC
Thanks to Kit Baum, a program -kaplansky- has been posted on SSC.
Stata 8 is required. You should instsll with -ssc- if interested.
-kaplansky- is a revision of a program posted on 10 May in
a thread on whether generated normal (Gaussian) distributions
really do have skewness 0 and kurtosis 3 (with the definitions
of those measures used by -summarize-):
The name -kaplansky- is easily explained. -kaplansky-
graphs some examples of distributions with various values of
kurtosis discussed by Kaplansky in 1945. The intent is cautionary:
values of kurtosis higher and lower than the Gaussian or normal value
are consistent with various peak and tail properties.
The program now posted is more versatile than that posted on 10
May and there is, naturally, now a help file with details of
the distributions in question and a vignette, Stata manual-style,
on Irving Kaplansky (1917-2006).
A vein in the literature centres on the rather fuzzy question
"What is kurtosis?". Many people want it to mean one thing they can
wrap their mind around (peakedness, say), but one of Kaplansky's
maxims was to look at examples as a way of saving yourself from
misunderstandings. He didn't plot his densities, but that's something
that's easily done.
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