Re: st: general statistical reasoning question in biomedical statistics (no Stata content)

[Mike Lacy <Michael.Lacy@colostate.edu>]

statistics (no Stata content)

Having read the Statalist FAQ, and previous correspondence about general
statistical questions, I hope no one minds . . . .

>Among my teaching duties in my medical school and family practice
>residency is "critical appraisal of the medical literature."  I try to
>go over principles of good design and valid analysis.  A question
>frequently comes up when we discuss randomized controlled trials.  In
>these articles, there is almost always a "Table 1," that describes the
>baseline demographic and clinical variables of the two arms (say,
>placebo and active drug, for example.)  There are usually *a lot* of
>baseline measurements.  Each one is usually listed with a "P value,"
>indicating whether the placebo and active drug subjects differed on that
>measurement.

 I would agree in thinking this a misguided practice. First of all, it 
implicitly rests on and reinforces the notion that a small p-value 
indicates an important difference. Secondly, as K. Rothman noted somewhere 
(and I believes demonstrates with a simple example--can't remember), 
whether the difference ab initio is "significant" is a different matter 
than whether it is large enough to cause problems with assessing the 
treatment effect in a randomized trial.

Regards,

Regards,
=-=-=-=-=-=-=-=-=-=-=-=-=
Mike Lacy
Fort Collins CO
(970) 491-6721 office





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