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Re: st: Sample Size Calcs, Multiple testing and CI's

From   Ronan Conroy <>
To   "" <>
Subject   Re: st: Sample Size Calcs, Multiple testing and CI's
Date   Wed, 25 Feb 2009 12:49:36 +0000

On 25 Feabh 2009, at 10:18, wrote:

I'm trying to come up with a sample size calculation for a proposed patient study which has fourteen equally important endpoints - different quality of
life measures (assume all continuous). All endpoints involve the same
patients being statistically compared against published norm values (t
tests). Each of these norm values themselves have come from a different
study (14 in all - one for each providing norm mean, SD and Nnorm).

The recommendation would be not to do this at all. A trial should have one primary endpoint, which should be adequately powered (90% or better).

The problem of multiple tests of the same hypothesis cannot be solved statistically. It's a methodological flaw. Aside from everything else, a trial with 14 different measures of quality of life will suffer from poor data quality because of the sheer volume of information being gathered from participants.

The investigators should stop dithering, pick and good quality of life measure and get on with it.

Ronan Conroy
Royal College of Surgeons in Ireland
Epidemiology Department,
Beaux Lane House, Dublin 2, Ireland
+353 (0)1 402 2431
+353 (0)87 799 97 95
+353 (0)1 402 2764 (Fax - remember them?)

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