Re: Repeated measures ANOVA with one measurement

On Jul 11, 6:41 am, matt.goup...@xxxxxxxxx wrote:
A few quick questions about repeated measures ANOVA:

1) Is it possible to do a repeated measures ANOVA with just one
measurement per condition (theoretically speaking)?

Yes

2) Is it possible to do a repeated measures ANOVA with just one
measurement per condition in SPSS v 15.0?

Yes

3) If yes to either 1 or 2, does this make any sense?

Yes

4) Would there be a difference between a repeated measures ANOVA with
one measurement and an ANCOVA?

Yes

Thanks,
mg

I assume that by "having only one measurement per condition" you mean
that each subject is measured once for each condition, so for, say, 10
subjects and 3 conditions you have 30 measurements total. If either of
the 10/3 above is 1, then I take back the 'yes'es. Such a setup is the
most common situation for repeated measures ANOVA, so any reasonable
statistical software will have it. In some cases it is useful to know
that mathematically a one-way repeated measures ANOVA is the same as a
two-way (regular) ANOVA without an interaction term, and at least the
latter is surely implemented in SPSS (which I have never used).
The fact that you are asking about ANCOVA implies that your conditions
are described by a continuous variable (time?). The repeated measures
ANOVA will not take into account the ordering and will not "smooth
out" the effect of close-by values of the covariate. On the other
hand, classic ANCOVA will impose a linear effect (which takes into
account the order and smoothes), which might be inappropriate if the
effect is non-linear. But if a linear model in the covariate fits
well, ANCOVA will have more power.

Hope it helps,
Aniko

.

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