[R] P values
Robert A LaBudde
ral at lcfltd.com
Fri May 7 01:09:01 CEST 2010
At 01:40 PM 5/6/2010, Joris Meys wrote:
>On Thu, May 6, 2010 at 6:09 PM, Greg Snow <Greg.Snow at imail.org> wrote:
> > Because if you use the sample standard deviation then it is a t test not a
> > z test.
>I'm doubting that seriously...
>You calculate normalized Z-values by substracting the sample mean and
>dividing by the sample sd. So Thomas is correct. It becomes a Z-test since
>you compare these normalized Z-values with the Z distribution, instead of
>the (more appropriate) T-distribution. The T-distribution is essentially a
>Z-distribution that is corrected for the finite sample size. In Asymptopia,
>the Z and T distribution are identical.
And it is only in Utopia that any P-value less than 0.01 actually
corresponds to reality.
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral at lcfltd.com
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
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