Note on Knight's Analysis of the Wais—III Instruction Effect on the Matrix Reasoning Subtest
Knight's 2003 analysis of the effect of the WAIS–III instructions on the Matrix Reasoning subtest was based on multiple t tests, which is a violation of conventional statistical procedures. Using this procedure significant differences were found between the group who know the subtest was untimed versus the group which did not know if the subtest was timed or untimed. Reanalysis of the data used three statistical alternatives: (a) Bonferroni correction for all possible t tests, (b) one-way analysis of variance, and (c) selected t tests with the Bonferroni correction. All three analyses yielded nonsignificant differences between means, thereby changing the conclusions of Knight's study.