I’ve performed a quick multidimensional scaling analysis for the items of the C-10. The study is based on very few subjects (N=42) and has to be taken carefully.
The C-10 is prepared with 20 verbal analogies, 20 numerical sequences and 20 word similarities. With such a difference in items along with the small sample size, a Guttman effect (1955) wasn’t expected to be shown. However, as can be seen in Figure 1, a horse-shoe shape appeared even if the inadequacies are not perfect for a two-dimensional solution (STRESS=.30, RSQ=.66) -which is quite logical-.
Of course, it would be too early to draw conclusions out of these preliminary results, but one can make the assumption that even if the items apply different cognitive abilities, they are sufficiently g-loaded for a continuum from the easiest to the hardest one to be shown in a two-dimensional Euclidean space.
References.
Guttman, L (1955). A generalized simplex for factor analysis. Psychometrika, 20, pp 173-192.
