In article <[EMAIL PROTECTED]>,
dennis roberts <[EMAIL PROTECTED]> wrote:
>i was not suggesting taking away from our arsenal of tricks ... but, since
>i was one of those old guys too ... i am wondering if we were mostly lead
>astray ...?
>the more i work with statistical methods, the less i see any meaningful (at
>the level of dominance that we see it) applications of hypothesis testing ...
>here is a typical problem ... and we teach students this!
>1. we design a new treatment
>2. we do an experiment
>3. our null hypothesis is that both 'methods', new and old, produce the
>same results
I presume you mean the same distribution of results.
But this is at least next to impossible. Even if all you are
doing is using a new batch of the same old material, there will
be SOME difference. This may or may not be important.
>4. we WANT to reject the null (especially if OUR method is better!)
Some do, and some do not.
>5. we DO a two sample t test (our t was 2.98 with 60 df) and reject the
>null ... and in our favor!
>6. what has this told us?
>if this is ALL you do ... what it has told you AT BEST is that ... the
>methods probably are not the same ... but, is that the question of interest
>to us?
>no ... the real question is: how much difference is there in the two methods?
>our t test does NOT say anything about that
>1 to 6 can be applied to all sorts of hyp tests ... and most lead us
>essentially into a dead end
One should approach the problem as a decision problem form
the beginning. The real main question is, should the new
treatment be used? There are many variations on this, and
what may be the least useful action is to say either that
there is a statistically significant difference, OR that
there is no difference. It is easy to give reasonable
examples where either variation of the current method is
the opposite of what is wanted.
--
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
===========================================================================
This list is open to everyone. Occasionally, less thoughtful
people send inappropriate messages. Please DO NOT COMPLAIN TO
THE POSTMASTER about these messages because the postmaster has no
way of controlling them, and excessive complaints will result in
termination of the list.
For information about this list, including information about the
problem of inappropriate messages and information about how to
unsubscribe, please see the web page at
http://jse.stat.ncsu.edu/
===========================================================================
