The psychopathology of everyday art: a quantitative Study - World ...

the most interpretable studies from 20 years review of the literature; and (ii) is answered
through the interpretation of the discriminant analysis performed on the collected data
from patients and controls.
(i) Is the DAPA a better assessment than the other tests reviewed in Chapter 2?
In order to contrast the effect from the DAPA with that of the general tenor of the
literature, the basic differences in effect size between controls and patients on each
variable from the DAPA were determined by another t-test. Each variable was treated
as though it was independent, purely for the theoretical comparison. These tests cannot
be regarded in practice as independent, as there were obvious correlations in the data and
so there was likely to be confounding errors, due to multicollinearity -one variable may
be the main predictor, subsuming those correlated with it to insignificant contributions,
thus true results for the DAPA should take account of direct relations between variables.
(ii) Can the DAPA practically discriminate between patients and controls.
Regression analysis was not applicable to this study because from the discussion of
results it was obvious that there could be interactions and correlations between one or
more of the predictor variables. The more complicated regression techniques require more
cases. The discriminant analysis is an older technique, but for 2 groups gives a similar
result. Discriminant analysis avoids the problem of multicollinearity by setting a
tolerance level which excludes variables that are highly correlated with each other. In
Chapman and Hall, p.211.
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