At 01:40 PM 5/6/2010, Joris Meys wrote:
On Thu, May 6, 2010 at 6:09 PM, Greg Snow <greg.s...@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: r...@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
"Vere scire est per causas scire"
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
