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st: Re: Sample size to detect a rare response


From   Paddy Woodburn <paddywoodburn@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: Sample size to detect a rare response
Date   Mon, 30 Nov 2009 09:18:54 -0800 (PST)

Dear Statalist,

I apologise; I was forgetting basic algebra.  All I had to do to calculate the necessary number was to figure out that the power = 1-((1-P)^n), where n is the number of people you'd need to sample.  Best regards,

Paddy


----- Original Message ----
From: Paddy Woodburn <paddywoodburn@yahoo.co.uk>
To: statalist@hsphsun2.harvard.edu
Sent: Mon, 30 November, 2009 15:57:13
Subject: Sample size to detect a rare response

Dear Statalist,

If you wanted 90% power to detect at least one positive result for a rare condition (expected proportion P) in a population, how would you calculate how many people you would need to test?  Is there a command for this?

Best regards,

Paddy


      

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