Hi folks,
I would argue that random assignment is only a means to an end, the
end being having at least two groups that are assumed to be roughly equal on
all variables. Seen that way, a within-subjects design is simply another
means of achieving the same end. I understand the limitations, but would
argue that with appropriate counter-balancing these can be overcome. This
may be an argument of convenience for me or a result of dissonance-reduction
on my part; we have a very small subject pool and strongly encourage
within-subject designs where possible
Joe Hatcher
Ripon College
Ripon, Wi 54971 USA
[EMAIL PROTECTED]
> ----------
> From: Mike Scoles
> Reply To: Teaching in the Psychological Sciences
> Sent: Wednesday, February 26, 2003 11:31 AM
> To: Teaching in the Psychological Sciences
> Subject: RE: We've got it all wrong
>
> I'm going to stick with Sir Fisher and reserve the term "experiment" for
> situations where there is random assignment to conditions. I do not know
> of
> any within-subjects designs that would not be better as mixed designs.
> Within-subject designs are too easily compromised by history, maturation,
> instrumentation, attrition, and (sometimes) test sensitization and
> regression issues. Let's see, the only one of the "Big 7" that I left out
> was subject selection--the major problem with quasi-experiments. Of
> course,
> good quasi-experiments can provide information as useful as a marginal
> experiment.
>
> Notice that many texts discuss quasi-experiments and single-subject
> designs
> in the same context. Even though many people would consider
> single-subject
> designs to be true experiments, they have many of the same flaws as
> quasi-experiments. These flaws can be minimized by careful attention to
> control of extraneous variables, but that doesn't make them true
> experiments
> in Fisher's sense.
>
> *************************************************
> Michael T. Scoles, Ph.D.
> Director, Arkansas Charter School Resource Center
> Associate Professor of Psychology & Counseling
> University of Central Arkansas
> Conway, AR 72035
> voice: (501) 450-5418
> fax: (501) 450-5424
> *************************************************
>
>
>
>
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