To comment and question some of Dr. Allison's insight:
>>My understanding of the arbitrary "line in the sand" of 0.05 was
>>originally due to the choice of the original tables (pre computer)
I have heard this too. It was very tedious to calculate probabilities (pre
Personal Computer) as is done now, so the investigator would pick the
appropriate values to simplify the calculations.
>>The p value reflects the probability of the observed change happening by
chance.
Isn't this only correct if the null hypothesis is correct (not
rejected?). This is why (as explained to me by statisticians - I won't
claim authority here) it is considered incorrect to differentiate
"significant" from "very significant" from "highly significant"? I present
this point because of your comment about relating the alpha level to the
seriousness of the outcome.
Bryan Kirking
ProbaSci LLC
tel. 512.218.3900
fax. 512.218.3972
www.probasci.com
bryan@probasci.com
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