Dennis Roberts wrote:
> if you are interested in the relationship between heights and weights of
> people, in the larger population ... the notion that we test this against
a
> null of rho=0 is not credible ... in fact, it is rather stupid ... a more
> sensible null would be perhaps a rho of .5 ...
No.... if you have to start "a more sensible null would be perhaps" you
almost surely do not have a hypothesis worth testing. Put it this way:
If your possible outcomes are
"The correlation is not zero"
or "The correlation may be zero"
these are both weak statements but you might not feel silly making either of
them. (If you would, then use an interval estimate instead!)
"The correlation is not 0.5"
or "The correlation may be 0.5"
both leave the listener wondering "why 0.5?" If the only answer is "well,
it was a round number close enough to x bar [or "to my guesstimate before
the experiment"] not to seem silly, but far enough away that I thought I
could reject it." then the test is pointless.
-Robert Dawson
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