> The sleep/mortality study does have a very large sample size which is
always
> good. However, I always worry about studies which look at so many
variables
> from the very beginning. It's not so much a hypothesis proving exercise,
> more of a fishing trip...

Yes, Certainly doesn't prove or even suggest causality. Perhaps people
wholiove longer sleep less. Perhaps ...

> Thinking of the association problem, I remember my teacher in critical
> reading telling us of the association between increased stork numbers and
> increased new born babies after WWII. It even proves a long held belief :)

In this case an obvious correlation suggests itself - the end of the war
would have created a more benign and hopeful environment for both species.
Then again, it could be that ... :-)



        RM

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