In article <[EMAIL PROTECTED]>,
Paul W. Jeffries <[EMAIL PROTECTED]> wrote:
>Robert Dawson said that one of his approaches to dealing with z test is to
>treat it as a historical anecdote. I like that approach and must give it
>a try.
It is almost the other way around. The z test comes up as
an approximation based on the central limit theorem, in cases
in which it was appropriate. Both of these tests are not at
all sound unless one can believe in the PRECISE null hypothesis.
The z test, if the conditions are approximately satisfied, is
much more robust than the t test. The convergence of the
distribution of the sample variance to the chi squared
distribution is likely to be worse than that of the sample
mean to the normal distribution.
--
This address is for information only. I do not claim that these views
are those of the Statistics Department or of Purdue University.
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
[EMAIL PROTECTED] Phone: (765)494-6054 FAX: (765)494-0558
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