Re: Flip side of Fisher Exact

Tim Witort seemed to utter in news:Xns9699617C88AE8timwitortwrotethis@
207.217.125.201:

> I have a given 2x2 matrix on which I perform a Fisher Exact.
> This is a fictional example of the response of Dogs and Cats
> when they are presented with a particular bowl of food.
>
> eat don't eat
>
> Dogs 7 0
>
> Cats 1 8
>
> One-tailed Fisher gives p=0.0007. From what I understand,
> this indicates the probability that these cell frequencies
> or "worse" could occur. Can I subtract p from 1.0 to
> obtain the opposite - the likelihood that these frequencies or
> "better" could occur? Or does Fisher not allow that?

Just some clarification as to why one might want to do this (subtract
the Fisher result from 1)...

If H_0 was that dogs and cats would be equally attracted to the
food, it would appear that we can reject that. And if H_0 was
that dogs are not more repulsed by the food than cats, it would
appear we can reject that. But if I want to present a numerical
result of the probability that dogs are more repulsed by the food
than cats, can I subtract Fisher from 1 to get this? The more
I think about this the more I suspect that I cannot do this.
I am left with the quandry of having a pretty obvious result
that dogs are *not* more repulsed than cats, but I have no numerical
result to present.

The reason I cannot just present the 0.0007 value is that the
results of many foods are presented at one time. And if the
matrix above were exactly reversed (dogs mostly not eating and
all cats eating), Fisher would give the same result, but it
would mean the exact opposite thing regarding dogs' attraction
to the food. So I would like to differentiate the results
that show dogs' attraction and repulsion to the foods compared
to cats.

-- TRW
_______________________________________
t r w 7
at
i x dot n e t c o m dot c o m
_______________________________________
.

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