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

finished the set. They were asked for their comments and suggestions. Most
participants took about 10 minutes for the whole process as described in the DAPA
rating guide (Chapter 3) per painting by the end.
Analysis: treatment of the data
A point by point comparison of every category per gridsquare would have been
ridiculously long and complicated. The propriety of different methods of agreement are
discussed at the end of Chapter 2 (reliability). Altman 270 recommends Kappa for
categorical variables, and warns against the misapplication of the correlation coefficient
to measure agreement for categorical scales. However, a disadvantage of kappa is that it
takes no account of disagreements and is not useful for numbers of raters, numbers of
categories, non-ordinal scales and large tables, often requiring considerable collapsing of
the data and thus not for this study. A categorical comparison was therefore both
unwieldy and unnecessary, since it is the final mean score, used as continuous data,
which is the hub of the DAPA process. The questionable propriety of the correlation co-
efficient for analysis of agreement, as expounded by Altman, is that although it indicates
linear association, how nearly the scores are ordered in the same way, it does not indicate
whether the level of the scores have changed. This is important because ordinal
positioning is not relational and therefore particularly makes nonsense of categorical
correlations.
270
D.G. Altman (1994), Practical Statistics for Medical Research , London, 7th ed. originally 1991:
Chapman Hall, p.284, and 409.
219