Johannes Hartig wrote:
> (1) Where does the standard error I get from SPSS come
> from? I think it should be a simple formula, but I don't find
> it...
An approximation is sqrt(6/n)
>From SPSS algorithms, SE of Skewness is
sqrt( (6 * n * (n - 1)) / ( (n - 2) * (n + 1) * (n + 3) )
where n is the sample size.
> (3) SPSS online help says "A skewness value greater than 1 generally
> indicates a distribution that differs significantly from a normal
> distribution.". Why this?
My guess is that it is because for any sample size greater than about
20, Skew >=1 / SE of Skew is going to lead to z values greater than
1.96.
HTH,
Chuck
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Chuck Cleland
Institute for the Study of Child Development
UMDNJ--Robert Wood Johnson Medical School
97 Paterson Street
New Brunswick, NJ 08903
phone: (732) 235-7699
fax: (732) 235-6189
http://www2.umdnj.edu/iscdweb/
http://www.home.earthlink.net/~ccleland/
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