Richard A. Beldin wrote:
>
> R A Fisher showed that random assignment of treatments to subjects from
> "almost any population" generates a proability distribution of treatment
> differences which satisfies the assumptions of ANOVA Random sampling of
> the population is not required but extrapolation to populations not
> studied is risky, of course.
An excellent summary.
Random sampling from a specifiied population is (nigh on) impossible unless
you have a finite, proximate target population in mind (e.g., a specific pool
of voters, consumers or whatever).
Extrapolation or generalization will always be tricky. For example, imagine I
could randomly sample from everyone on the planet. I'd still have problems
trying to generalize those findings to people alive in 10 or 50 years time (or
in the past).
Generalization has to rely heavily on theory and domain knowledge no matter
how good the stats.
Thom
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