Re: Comparing 2 groups of variables [SEC: UNCLASSIFIED]

[Gosse, Michelle]

Hi all,

 

This is striking me as a psychometric question rather than a purely statistical question. I suggest looking at how the individual items (attributes) are performing compared to each other on aspects such as discrimination of subgroups. Dropping items based on a relatively gross measure of all subject test performance may lead you to drop items that discriminate a low-population group, and are therefore useful under certain circumstances.

 

An 11-point scale seems rather large (assuming this is a social sciences device). I wonder how this affects score and item reliability.

 

UNCLASSIFIED

From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Mark W. Andrews
Sent: Thursday, 15 December 2011 8:14 AM
To: [hidden email]
Subject: Re: Comparing 2 groups of variables

 

I have 17 attributes (11 point scale). We want to reduce it to 10 attributes. Someone asked how much we are losing by reducing the number of attributes. I was thinking that the math would be similar to the accumulated variance explained figures you get from a factor analysis. Instead of factors, however, I would be looking at attribute variables.

 

From: Poes, Matthew Joseph [hidden email]
Sent: Wednesday, December 14, 2011 2:05 PM
To: Mark Andrews ([hidden email]); [hidden email]
Subject: RE: Comparing 2 groups of variables

 

Can you give more detail?  Are you saying that you have a group of, say, 5 predictor variables, and you want to know what the association is of those 5 variables on an outcome variable Y, and then what total variance is explained by 3 of the 5 variables, while still accounting for the common variance in the other two variables?  Or are you asking what amount of variance in a group of 5 variables is explained by a separate group of 3 variables?  Or, are you asking this in more scalar terms, and wanting to know which variables account for the greatest amount of variance within the collective latent variable that they collectively make up.  In the latter, we have the same 5 variables, combined and they explain mood stability, and you want to know what amount of the total explainability 3 of the 5 variables have?  Thanks.

 

Matthew J Poes

Research Data Specialist

Center for Prevention Research and Development

University of Illinois

 

From: SPSSX(r) Discussion [hidden email] On Behalf Of Mark W. Andrews
Sent: Wednesday, December 14, 2011 12:49 PM
To: [hidden email]
Subject: Comparing 2 groups of variables

 

I am trying figure out how much of the variance within a group of variables is explained by the a subgroup of variables. Can anyone point me in the right direction?

 

Mark W. Andrews
Senior Study Director
Synovate 
7600 Leesburg Pike, East Building, Suite 110
Falls Church, VA 22043
Phone   [phone]
FAX      [phone]
Email    [hidden email]
Web     www.synovate.com

 

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