Posted by
Vaughan, Christopher on
Sep 16, 2011; 4:20pm
URL: http://spssx-discussion.165.s1.nabble.com/Building-a-hybrid-regression-model-incorporating-intraclass-correlation-tp4810791p4811561.html
Great point of clarification Bruce, and thank you.
Yes, the intention is to build a prediction model in order to guide
decisions about reliable change. It is in fact the exact same variable
that we are measuring twice in the same person that we want to assess.
It seems that in this situation, the ICC is more appropriate measure of
association (rather than a Pearson r) but it is not typically used in a
regression model. Does this make sense, and if so, how do we build a
model that would include it?
Thanks,
CV
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of
Bruce Weaver
Sent: Friday, September 16, 2011 12:06 PM
To:
[hidden email]
Subject: Re: Building a hybrid regression model incorporating intraclass
correlation
It seems to me that there are (at least) two different uses of the ICC.
1. It is used as a reliability coefficient (e.g., see Health Measurement
Scales by Streiner & Norman).
2. It is used in the way Garry describes, where it is often called the
intra-cluster correlation.
For the first use, one should have the same variable measured twice (in
the
same units) IMO.
Cheers!
Bruce
Garry Gelade wrote:
>
> 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: (202)
> 476-2429
>
> Neuropsychology Dept: (301) 765-5430
>
> Fax: (301) 765-5497
>
-----
--
Bruce Weaver
[hidden email]
http://sites.google.com/a/lakeheadu.ca/bweaver/"When all else fails, RTFM."
NOTE: My Hotmail account is not monitored regularly.
To send me an e-mail, please use the address shown above.
--
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