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Re: st: Sample size calculation


From   Ronán Conroy <rconroy@rcsi.ie>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Sample size calculation
Date   Wed, 26 Oct 2005 16:01:52 +0100

On 26 DFómh 2005, at 14:19, <slaowattana@pol.net> <slaowattana@pol.net> wrote:


We are planning to measure some cytokines in patients with MS comparing
between a group with treatment and control, but there have not been
literatures regarding these measurements, so we do not have an estimated
mean and standard deviation. Is there a way to estimate a sample size?
(our IRB really wants to see sample size estimate.) Thanks.


You really are in the dark, then.

There are several approaches. The Resource Equation method

http://embryo.ib.amwaw.edu.pl/invittox/er/ER/ER%2029.pdf see page 9

is useful in a preliminary experiment. It's based on the idea that the amount of information in each new piece of data diminishes as the sample size increases.

It allows you to estimate the sample size needed to ascertain whether a study would be useful or not. It is often used in animal research where investigators have no idea at all of what they might find.

Ronán Conroy
rconroy@rcsi.ie




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