On Wed, 28 Feb 2001, Mike Granaas wrote in part (and 2 paragraphs of
descriptive prose quoted at the end):
> ... is there some method that will allow him to get the prediction
> equation he wants?
Probably the best approach is the multilevel (aka hierarchical) modelling
advocated by previous respondents. Possible problems with that approach:
(1) you'll need purpose-built software, which may not be conveniently
available at USD; (2) the user is usually required (as I rather vaguely
recall from a brush with Goldstein's ML3 a decade ago) to specify which
(co)variances are to be estimated in the model, both within and between
levels, and if your student isn't up to this degree of technical skill,
(s)he may not have a clue as to what the output will be trying to say.
For a conceptually simpler, if less rigorous, approach, the problem could
be addressed as an analysis of covariance (to use the now old-fashioned
language), using the intended predictor as the covariate and the 10 (or
whatever number of) trials for each S as a blocking variable (as in
randomized blocks in ANOVA). This would at least bleed off (so to write)
some of the excess number of degrees of freedom; especially if one also
modelled interaction between predictor and blocking variable (which might
well require a GLM program, rather than an ANCOVA program), as in testing
homogeneity of regression. The blocking variable itself might be
interpretable (if one were interested) as an (idiosyncratic?) amalgam of
practice/learning and fatigue.
-- Don.
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Donald F. Burrill [EMAIL PROTECTED]
348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED]
MSC #29, Plymouth, NH 03264 (603) 535-2597
Department of Mathematics, Boston University [EMAIL PROTECTED]
111 Cummington Street, room 261, Boston, MA 02215 (617) 353-5288
184 Nashua Road, Bedford, NH 03110 (603) 471-7128
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The situation as Mike desribed it:
> I have a student coming in later to talk about a regression problem.
> Based on what he's told me so far he is going to be using predicting
> inter-response intervals to predict inter-stimulus intervals (or vice
> versa).
>
> What bothers me is that he will be collecting data from multiple trials
> for each subject and then treating the trials as independent replicates.
> That is, assuming 10 trials/S and 10 S he will act as if he has 100
> independent data points for calculating a bivariate regression.
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