On 25 Feabh 2009, at 10:18, [email protected] 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
=================================
[email protected]
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?)
http://rcsi.academia.edu/RonanConroy
P Before printing, think about the environment
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
