We don't really disagree. Any apparent disagreement is probably due
to the abbreviated kind of discussion that takes place in Usenet.
See http://www.tufts.edu/~gdallal/onesided.htm
Alan McLean ([EMAIL PROTECTED]) wrote:
> My point however is still true - that the person who receives
> the control treatment is presumably getting an inferior treatment. You
> certainly don't test a new treatment if you think it is worse than
> nothing, or worse than current treatments!
Equipoise demands the investigator be uncertain of the direction.
The problem with one-tailed tests is that they imply the irrelevance
of differences in a particular direction. I've yet to meet the
researcher who is willing to say they are irrelevant regardless of
what they might be.
> For the sample data I compute xbar (the difference of sample means if
> there is a control group). There are three possibilities.
>
> 1. xbar is negative
> If 1 does happen, we would conclude either that the new treatment is no
> better than the control, and may be worse. In either case we junk the
> new treatment.
The question is, do you look to see how much worse? If the answer
is no, then I've no argument. But everyone looks. It's unethical not
to!
--Jerry
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