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Date:         Mon, 14 Jun 2010 10:57:16 -0400
Reply-To:     Ryan Black <ryan.andrew.black@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Ryan Black <ryan.andrew.black@GMAIL.COM>
Subject:      Re: when to do separate analysis for gender
In-Reply-To:  <279E0CB25CBDEF4DB4A50E89328780E2019F7CEC@CHEXCMS08.one.ads.che.org>
Content-Type: text/plain; charset=ISO-8859-1

Kevin,

Could you provide a reference for retaining interaction terms that have p-values =<.25?

Thanks!

Ryan

On Mon, Jun 14, 2010 at 10:49 AM, Viel, Kevin <kviel@sjha.org> wrote:

> > -----Original Message----- > > From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of > Myung > > Ki > > Sent: Monday, June 14, 2010 8:42 AM > > To: SAS-L@LISTSERV.UGA.EDU > > Subject: when to do separate analysis for gender > > > > Hello everybody, > > > > I have a question on when we need to do separate analysis and when to do > > combined analysis. > > To decide this, we have done descriptive analysis by gender and test many > > interaction by gender term as well. > > But the results were not straightforward for that decision. > > > > I prefer to do separate analysis complemented by gender interaction. This > > is > > because although combined analysis is able to present estimates for sex > > variable, which separate analysis cannot, it doesn't allow comparison > > between gender with values. But others in my group think differently. > > > > So I would like to your opinion and possibly a reference on this issue, > > Any comments will be appreciated. > > Myung, > > We need much more information. For instance, your model and a brief > description of study design. The "interaction" might not sufficiently be > handled by inclusion of the term "sex*exposure". How you code the terms > could be a problem. > > I think separate analyses are justifiable as the more conservative > approach. Remember, that you can model a circle with a triangle, but the > fit might not be the best. Sex as a dichotomous variable, to me, is always > questionable, but how objectionably so depends on the study question. > > Note that I used the term sex and you used gender. I made an assumption. > I prefer gender as a behavioural construct and sex as a physical one. > Despite being classically treatment as a dichotomous trait, sex is not male > or female on a refined level. For instance, X0 (Turner's syndrome) and XXY > (Klinefelter's syndrome) occur more frequently than some might expect. > Also, the levels of "sex" hormones do not always accurately classify > physical or karyotypic sex. However, as measurements of sex hormones or > other traits are rarely done, we are usually stuck with female and male sex. > > By the way, I have seen recommendations that p-values, if you will, on > interaction terms as high as 0.25 should mean that the term should be > retained in the absence of a (strong) a priori argument. > > -Kevin > > > > Kevin Viel, PhD > Senior Research Statistician > Patient Safety & Quality > International College of Robotic Surgery > Saint Joseph's Translational Research Institute > > Saint Joseph's Hospital > 5671 Peachtree Dunwoody Road, NE, Suite 330 > Atlanta, GA 30342 > > (678) 843-6076: Direct Phone > (678) 843-6153: Facsimile > (404) 558-1364: Mobile > kviel@sjha.org > Confidentiality Notice: > This e-mail, including any attachments is the > property of Catholic Health East and is intended > for the sole use of the intended recipient(s). > It may contain information that is privileged and > confidential. Any unauthorized review, use, > disclosure, or distribution is prohibited. If you are > not the intended recipient, please delete this message, and > reply to the sender regarding the error in a separate email. >


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