Date: Mon, 8 May 2006 12:38:39 -0400
Reply-To: wraong <wrong.wang@GMAIL.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: wraong <wrong.wang@GMAIL.COM>
Subject: Re: help on power calculation
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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 <Jiann-Shiun.Huang@amerus.com> wrote:
> 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
> fax 1-515-557-2422
> >>> Wrong Wang <wrong.wang@GMAIL.COM> 05/08/06 11:16 AM >>>
> Hi, all
> I am asked to do power calculation for a case-control study, the
> sizes are equal in the two groups. I will compare the upper quartile
> to the lower quartile group.
> I know I can use proc power in SAS to calculate power for a normal
> control study, which given prevalence of exposure in control group. But
> the above condition, I don't think it's correct to just set prevalence
> exposure in control group as 0.25.
> So I need your help on how to solve such problem.