Response embedded within message:
In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] wrote:
>
> The way this world is ---
> A master's candidate, or a phD candidate, or a professor,
> or a working scientist, has put a lot into his project.
> In terms of time, in terms of money, and more important
> still, in terms of emotional commitment, (S)he has lived
> with this project for two years or more.
>
> That is a source of subjective bias: (S)he WANTS the data to
> show something, preferably to support the original idea behind
> the research, but even failing that, to show something.
>
> There needs be an objective brake on this wish. An hypothesis
> test is that a brake. NOT rejecting the null hypothesis means
> that the data has no information (about whatever aspect of the
> data the test was designed to look at), STOP THERE; go no
> further.
I hope not to get too off topic here, but sometimes the failure to
reject the null hypothesis has more implications than successfully
rejecting it. I understand your point here, and certainly have seen it
happen both personally and in the literature. However, as long as the
experiment has a sufficient sample size to detect a meaningful effect
(not necessarily just a null of an effect size of zero), then there is
something to say. For example, the literature has been overflowing with
reports of "estrogenic compounds" such as DDT/DDE that affect sexual
development of exposed animals. If someone found that DDE has little
ability to competitively bind to estrogen receptors (which someone has
found), at least to an extent necessary to elicit strong estrogenic
activity, this would not only mean that the null hypothesis that DDE is
estrogenic was rejected, but that something ELSE must be happening; ie.
that the known alterations to sexual development after exposure to DDE
is not due to estrogenic actvity. I am sure that this sort of thing must
be happening in other fields.
>
> Without some objective brake, the master's student, etc. will
> go ahead to say something about the data, even when the test
> would have told her(im) there is nothing to say.
Failure to reject null hypotheses that have been "successfully rejected"
in numerous previous experiments, and thus are generally accepted by the
scientific community at large, can have big implications, even if the
alternative explanations were not tested and thus remain unknown. It may
not happen often, but failure to reject a null hypothesis, particularly
one that was expected to be rejected, may indicate a poorly executed
study, but it may signal that the underlying theory from which the
experiment is based upon is wrong. That alone is valuable.
Shane de Solla
[EMAIL PROTECTED]
<snip>
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