Re: Building a hybrid regression model incorporating intraclass correlation

Posted by Garry Gelade on Sep 16, 2011; 3:09pm
URL: http://spssx-discussion.165.s1.nabble.com/Building-a-hybrid-regression-model-incorporating-intraclass-correlation-tp4810791p4811035.html

Dear Christopher

 

The term ‘intra-class correlation’ refers to grouped data and is a measure of the proportion of variance attributable to group membership.  It has nothing to do with the fact that the time1 test score is the” same type of variable” as the time2 test score.

 

For the analysis you are proposing, you can treat the time1 score in just the same way as age or gender, it is just another predictor of the time2 score.

 

Garry Gelade

 

From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Vaughan, Christopher
Sent: 16 September 2011 14:11
To: [hidden email]
Subject: Building a hybrid regression model incorporating intraclass correlation

 

Hello Everyone,

 

We am trying to tackle an issue related to developing a hybrid regression formula that combines both intra-class (i.e., correlating the same variable) and inter-class coefficients (e.g., Pearson) in the same regression model.  The purpose is to develop a regression line to predict Test Score at Time 2, using Test Score at Time 1 along with other demographic factors.   Our thought is that it is appropriate to use intra-class correlation coefficients in the model for the Time 1 Test Score (correlating the same type of variable), and when using various demographic factors (age, sex) variables in the prediction equation, the appropriate statistical method would be inter-class correlation as they are different variable types than the outcome variable (Test Score at Time 2). It is my understanding that the SPSS statistical models only use the Pearson - inter-class - method of relating predictor variables to outcome variables.

 

So here is where the question/ issue arises. The ultimate predictor variable, Test score at Time 1, is in fact an intra-class variable as it is the same type as the outcome variable, but we believe the SPSS regression methodology treats Test score at Time 1 statistically as an inter-class variable and calculates its correlation in the multivariate equation as inter-class. As a result, the prediction equation of the Outcome variable is using a lower test-retest coefficient and therefore generating a larger confidence band around the Test Score at Time 2 variable. It seems to us that this is not the appropriate statistical method.

 

First, is our argument appropriate/ cogent?

 

Second, if so, how do we correct the regression equation to be "hybrid" allowing intra-class correlation for the Test score at Time 1 variable, and inter-class for the other predictor variables?

 

Any and all of your thoughts would be much appreciated.

 

Thanks.

 

 

Christopher G. Vaughan, PsyD

Pediatric Neuropsychologist

Division of Pediatric Neuropsychology, Children's National Medical Center

Assistant Professor, Depts of Psychiatry and Behavioral Sciences & Pediatrics

The George Washington University School of Medicine

Safe Concussion Outcome, Recovery and Education (SCORE) Clinic: [phone]

Neuropsychology Dept: [phone]

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