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palestine

Re: sample size

thank you so much rehman for your resonse to my question.but i wonder if you have an idea bout some web sites that show some examples for sample size calculations.
thanx

asiddiqui

Re: sample size

A.S.A.

You need to consider the following:

(1) Event rate in control group.

(2) Relative treatment effect (ie difference in treatment effect between two groups).

(3) Type 1 error (also knows as alpha): usually 5% (a 5% chance we will conclude that there is a treatment group difference when, in truth, treatment is not better or worse than a placebo).

(4) Type 2 error (also knows as beta). Power of a study is 1-beta.

Try the following online calculators:

http://statpages.org/#Power

http://statpages.org/proppowr.html

If unsure, I suggest you get help from a medical statistician.

Good luck,

Rehman

palestine

sample size

Hi every body;
I just wonder if anybody knows the formulas used to calculate the sample size for a medical study.. or any web sites that clearly state how to calculate the sample size...
thank you