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Date:         Wed, 7 May 1997 10:07:43 -0400
Reply-To:     Ismail Parsa <iparsa@EPSILON.COM>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Ismail Parsa <iparsa@EPSILON.COM>
Subject:      Re: chaid on sas
Comments: To: ecm@NWU.EDU

|> From: Edward Malthouse <ecm@NWU.EDU> |> Subject: Re: chaid on sas |> |> I have used SPSS' version of CHAID and found it to be very dangerous. The |> problem I have with it is that it is prone to overfitting the data -- I get a |> nice tree and decent fit statistics, but when I apply it to another data set |> the predictions are not so good.

Tighten your stopping criteria and don't opt for a large/long tree.

|> I have had much better luck with Splus' CART (classification and regression |> trees is an improved version of chaid) functionality. It includes options

The two are not technically related. CART uses purity measures, like GINI index or entropy whereas CHAID uses chi-sqaure criterion in building trees.

|> that automate the process of validating the model with holdout samples.

You can certainly score a validation sample using CHAID.

Regards.

*-----------------------------* | Ismail Parsa | | Epsilon Data Management | | 50 Cambridge Street | | Burlington MA 01803 USA | | | | E-MAIL: iparsa@epsilon.com | | V-MAIL: (617) 273-0250*6734 | | FAX: (617) 272-8604 | | | | The Usual Caveat Applies | *-----------------------------*

|> |> I sincerely hope that SAS does not follow SPSS' model for CHAID. |> |> Ed Malthouse |> |> |> In article <19970430.161151.580850.NETNEWS@AUVM.AMERICAN.EDU>, |> "Zhang, Alex - O&MD NY" <OGILVY!OMDNY1!ZHANGAL@OMDNY.ATTMAIL.COM> wrote: |> >I was told at a SAS seminar about a month ago that CHAID and neural network |> >are only available through SI's Professional Service as part of the |> >customized packages. SI is planning to release a data mining product which |> >will include CHAID at the end of this year. A beta version may be available |> >as early as this Summer. |> > |> >Alex Zhang |> >Ogilvy & Mather Direct |> >alex.zhang@OGILVY.COM |> > ---------- |> >From: Philip Holland |> >To: Multiple recipients of list SAS-L; ZHANGAL |> >Subject: Re: chaid on sas |> >Date: Wednesday, April 30, 1997 4:54PM |> > |> >skmxx <skmxx@ibm.net> wrote: |> >>Hi! everyone. |> >> |> >>I need your advice. I want to run CHAID on sas, but, I cannot find |> >>where. In sas/stat manual I could not find any word CHAID on the index. |> >>I know there is CHAID option on spss. On sas where is this option or |> >>comparable option? I really appreciate your advice. |> >> |> >>Soo Hong Kim |> >>Graduate Student |> >>Syracuse Univ. |> > |> >I believe there are some SAS macros for CHAID stats |> >processing, supplied by the SAS Institute. I suggest you |> >contact your local SAS office, but be warned that they may not |> >be free... |> > |> >HTH..............Philip R Holland <phil.holland@bcs.org.uk> |> > Holland Numerics Ltd |> > Royston, Herts, UK |> > mobile: +44-(0)850-295556 |> |> Edward Malthouse |> Assistant Professor |> IMC Department |> Medill School of Journalism |> Northwestern University |> Evanston, Illinois |> ecm@nwu.edu |>


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