sofyan2000 wrote:
>
> I have conducted a repeated measure mixed two-factor ANOVA on one sample
> consisting of 2 groups (conservatives and liberals). The dependent variables
> where ATTA (attitude towards policy A) and ATTB (attitude towardfs B). I
> have a few questions:
>
> 1. What statistical ANOVA test can reveal an outlier in my data?
No statistical test can. If an outlier is defined as an observation from
outside the population you are interested in, the decision can only be made
with reference to the aims and context of the experiment. Statistical tests or
information can be use to help flag potential outliers, but that isn't the
same thing. If an outlier is defined as an unusually extreme observation which
may be distorting your test in some way you are better of use graphs and
diagnostic info to identify possible problematic observations. (In either case
running tests with and without potential outliers can be informative about how
they influence your analysis).
> 2. If my test failed the 'homogeneity of variance/ covariance' test, should
> I conduct a MANOVA ( learnt that this test does not require a homogeneity of
> variance/ covariance test)?
If you have a 2x2 mixed ANOVA homogeneity of covariance can not be violated
(and tests of sphericity can not be performed). Homogeniety of variance may be
violated, but better to look at graphs and descriptive statistics than rely on
tests (which may be radically over- or uner-powered). A common error is to
assume homogeneity of covariance/sphericity is violated if Mauchley's
sphericity test can not be computed (SPSS prints sig as "." when d.f. = 0).
> 3. Which part of the SPSS results (which heading?) afer running an MANOVA
> shows the interaction between the between groups IV (political category
> conservative vs. liberals) and the within-groups DV (ATTA & ATTB).
Tests of within-subjects effects, I believe.
Thom
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