Letter series and number series tests of items based on identical rules were administered to 160 male and 160 female undergraduates to determine comparability by testing equality of means, variances, and validity coefficients. Results indicate that letter and number series tests are not equivalent. Number series tests are easier, probably because…

This study evaluated the diagnostic validity of a task measuring abstract categorization ability in learning disabled (LD) and non-LD children. Data showed that the component of abstract category knowledge that best disciminates LD children from non-LD, is the knowledge of how members of abstract categories differ from each other. (Author/JAZ)