|Date: ||Fri, 27 Oct 2006 10:53:39 -0700|
|Reply-To: ||peter link <firstname.lastname@example.org>|
|Sender: ||"SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>|
|From: ||peter link <email@example.com>|
|Subject: ||Re: small sample-repeated predictors-more|
|Content-Type: ||text/plain; charset="US-ASCII"|
For your hypothetical example of many people observed many times, I would
recommend MIXED procedure (or some other software for Multilevel Modelling -
HLM, MLwin, MIXOR, SAS Proc Mixed, to name a few). To reiterate, linear
regression is not advised in this situation due to assumptions not being met
(non-independent observations, [E(ei * ej) does not equal 0].) If
interested in this approach see Singer & Willett, Applied Longitudinal Data
Analysis, Oxford University Press, 2003.
From: Rcarlstedt@aol.com [mailto:Rcarlstedt@aol.com]
Sent: Thursday, October 26, 2006 5:43 PM
To: Peter Link; SPSSX-L@LISTSERV.UGA.EDU
Subject: Re: small sample-repeated predictors-more
In a message dated 10/26/2006 8:18:01 PM Eastern Standard Time,
I wouldn't suggest doing linear regression on a single individual using
pre- and post. If you would do it this way, why not use all of the data
points, not just pre- and post-? That would make more sense to me.
The reason for this was that in the pre-condition HRV was only monitored
(5 predictor HRV measures), in the second post condition the player engaged
in an intervention that manipulated HRV while being monitored. In both cases
I wanted to find correlations between predictors and outcome measures and
variance explained through multiple regression and then compare differences
(i.e., was more of the variance explained in outcome on the basis of HRV
post compared to pre-no intervention).
Esentially, you are saying even if one has hundreds of measures obtained
through hundreds of measurement occasions that are hypothesized to predict
and correspond to specific outcome measures (each HRV data point corresponds
to an outcome [HRV-low frequency and say, batting result]) one should/cannot
validly use multiple regression to determine variance explained?
Roland A. Carlstedt, Ph.D.
Licensed Clinical Psychologist/Licensed Applied Psychologist
Clinical and Research Director: Integrative Psychological Services of NYC
Chair and Head Mentor: American Board of Sport Psychology
Research Fellow in Applied Neuroscience: Brain Resource Company