On 16 Nov 2000 17:18:44 GMT, [EMAIL PROTECTED] (Radford Neal)
wrote:
> In article <[EMAIL PROTECTED]>,
> Rich Ulrich <[EMAIL PROTECTED]> wrote:
>
> > There is another definition [ of "Type III error" ] cited a few
> > times which is seemingly technical, "rejecting the null, but in the
> > wrong direction". I think that is a similar sneer at bone-headedness.
> > There is no "wrong direction" with a two-tailed test...
>
> Are you really suggesting that researchers who reject H0: mu=0 with a
> two-tailed test act thereafter as if they know that mu is not zero,
> but have no idea whether it's positive or negative? I think this is
> highly implausible. Such "Type III" errors seems to me to be quite on
> a par with Type I and Type II errors.
>
Well, I can squint my eyes, and posit a Type III error that meets
that definition. But it's virtually never going to happen, or be
regarded as an event-of-that-class when it does; so it is not "on a
par with" the other two. In my opinion.
For that sort of Type III:
Here is a calcium-something-beta-blocker, for preventing some version
of heart disease, that was backed by a tiny amount of data analysis,
on top of a bunch of reasonable-sounding analogies. When the new
study came in, saying XX was bad instead of good, the media treated it
as an old, bad assumption, now (to some surprise) overturned. They
say, the old XX was never "well supported" in the first place.
I don't see how that gains coherence by ringing in "Type III."
If the old one was "well supported" after all, then we are not
talking about using the first really-good data to replace a minor
statistical artifact, as we were before. If it had been
well-supported, the new overthrow of XX did require some change in
QUESTION: or, so I presume.
I think that I could get lost here, without some examples of what
someone has in mind.
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
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