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Date:         Wed, 4 Jun 2003 16:15:49 -0300
Reply-To:     Alexandre Cechin <grothaal@hotmail.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Alexandre Cechin <grothaal@hotmail.com>
Subject:      Re: spss DUMMIE variables
Content-Type: text/plain; charset=iso-8859-1; format=flowed

Thanks Bin Fan, I will try to reduce the amount of independent variables as you say, as i allready tryed to run a model with more than 40 variables and it didnt work (the memory thing) .

But SPSS do accept this quantity od independent variables if you put only one variable (original with the 40 different values) and ask him to aply a contrast into it and set it as categorical into the dialog box. This way he makes "virtual Dummies" only for the procedure, but it enter the variable as a block, and not one at a time. The problem is that the procedure inputs all categories that way, and not only the significant ones.

My real question at this time is: there a big problem in letting the non significant ones into the model, is there a big change into final results?

>From: "Bin Fan" <fanb@childpsych.columbia.edu> >To: <grothaal@hotmail.com> >Subject: Re: spss DUMMIE variables >Date: Wed, 04 Jun 2003 14:43:13 -0400 > > >Alexandre Cechin: > >As my understanding is: >You have a variable which with 40 different categories, and you created 40 >New Dummy variables (0 or 1), and you want run >all the 40 dummy variables in Logistic Regression at same time. > >If that true, my answer is: YOU CAN NOT DO THAT IN SPSS. (Because there is >the limitation for the RAM on your computer). > >I did this before, the maximon of the independent variables is <=20 (if you >have thousands cases). > >YOU CAN TRY: >(1) Decrease your independent variables number: you can run linear >correlation between your dependent variable (1) and 40 independent > variables, and eliminate these not highly significant variables, and >keep less than 20 variables in Logistic Regression; > >(2) Run this one in SAS (Logistic Regression): Convert your SPSS data file >into SAS data file, and run same Logistic procedure in SAS. > >(3) Run this one in SUDAAN (Logistic Regression): Convert your SPSS data >file into SUDAAN or SAS data file, and run same Logistic > Regression in SUDAAN or SAS Callable SUDAAN: Logistic Dependent >Variable = 1 Independent Variable (with 40 categories), > SUDAAN will get the same result as SPSS or SAS (40 Variables). > >Do hope this will works for you. > >Best wishes. > > >Bin Fan >Columbia University > >*********************************************************************************************************************************** > > >>> Alexandre Cechin <grothaal@hotmail.com> 06/04/03 01:11PM >>> >Hi, > >Im using the logistic regression model in SPSS, and i have one variable >that >is categorical and have about 40 diferent categories. > >When apllying contrast, it run the model well, but all 40 categories are >tested as a block into the model. >This results in some coeficients that are significant at the .05 level and >others that are not. > >Is there any recomendation on what to do with these non significant >coeficients? I already tried to input these variables with manual >'dummiefication' but my SPSS does not support a large amount of variables >and cases (1million, that is already a subset from the universe of cases) >in >this procedure (memory overflow). > >Is it safe to let these non-significant categories into the model without >much 'damage' to the results? > > >Thanks all, > >_________________________________________________________________ >MSN Messenger: converse com os seus amigos online. >http://messenger.msn.com.br > >

_________________________________________________________________ MSN Messenger: converse com os seus amigos online. http://messenger.msn.com.br


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