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Date:         Mon, 8 May 2006 12:38:39 -0400
Reply-To:     wraong <>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         wraong <>
Subject:      Re: help on power calculation
Comments: To: Jiann-Shiun Huang <>
In-Reply-To:  <>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Thanks for your kind suggestion.

*Case-control study* is a retrospective observational study in which investigators identify a group of patients with a specified outcome (cases) and a group of patients without the specified outcome (controls). Investigators then compare the cases and the controls to determine possible factors which can be linked to the outcome.

On 5/8/06, Jiann-Shiun Huang <> wrote: > > Wrong: > > Is it possible we can describe in detail about case-control study so > that people like me without knowledge in the study could give a shot at > your problem? > > J S Huang > 1-515-557-3987 > fax 1-515-557-2422 > > >>> Wrong Wang <> 05/08/06 11:16 AM >>> > Hi, all > > I am asked to do power calculation for a case-control study, the > sample > sizes are equal in the two groups. I will compare the upper quartile > group > to the lower quartile group. > > I know I can use proc power in SAS to calculate power for a normal > case- > control study, which given prevalence of exposure in control group. But > in > the above condition, I don't think it's correct to just set prevalence > of > exposure in control group as 0.25. > > So I need your help on how to solve such problem. > > Thanks. >

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