Schematic demonstration of good and bad Construct Validity (CV) for 2
reference domains, each described by 3 tasks. Left: very good global CV,
performance of tasks within a reference domain are more similar
than between-reference domains. The Z-matrix reveals a
block-diagonal structure. The observed CV statistic, the difference of mean Z-
values within a reference ability to mean Z-values between reference ability
values quite high. Right: poor global CV, pairs of tasks within and between
reference domains show equal similarity, thus yielding CV value close to zero.
The diagonal elements in every Z matrix have been set to zero since for perfect
correlation Z becomes infinite.