On Sat, 14 Oct 2000 [EMAIL PROTECTED] wrote, inter alia:
> I *would* argue that without some method to determine the likelihood of
> a difference b/w two conditions you have no chance of determining
> practical importance at all.
But hypothesis testing procedures do not establish any such likelihood.
What they may establish is the likelihood of observing data like these,
IF the null hypothesis be true. That is not "the likelihood of a
difference between two [or more] conditions".
> But what if your power is very high and/or you have very large N? I
> have always found it surprising that we can't turn it around and
> develop a probability that two groups are the same. Power or beta is
> surely correlated with the certainty of this approach.
Again, we cannot "determine a probability that two [or more] groups are
the same". What we can do is determine the probability (beta) that we
could NOT reject the null hypothesis, IF the true state of affairs be a
specified degree of departure from the null hypothesis [of, presumably,
no difference].
(Or, if you prefer, the probability (power) that we COULD reject
the null, given that degree of departure from it.)
-- DFB.
----------------------------------------------------------------------
Donald F. Burrill [EMAIL PROTECTED]
348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED]
MSC #29, Plymouth, NH 03264 (603) 535-2597
Department of Mathematics, Boston University [EMAIL PROTECTED]
111 Cummington Street, room 261, Boston, MA 02215 (617) 353-5288
184 Nashua Road, Bedford, NH 03110 (603) 471-7128
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