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
Comments: To: Jiann-Shiun Huang <Jiann-Shiun.Huang@amerus.com>
In-Reply-To:  <s45f2c89.081@mail6.amerus.com>
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 <Jiann-Shiun.Huang@amerus.com> 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 <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
> 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.
>