Robust and powerful nonorthogonal analyses

Numerous types of analyses for factorial designs having unequal cell frequencies have been discussed in the literature. These analyses test either weighted or unweighted marginal means which, in turn, correspond to different model comparisons. Previous research has indicated, however, that these analyses result in biased (liberal or conservative) tests when cell variances are heterogeneous. We show how to obtain a generally robust and powerful analysis with any of the recommended nonorthogonal solutions by adapting a modification of the Welch-James procedure for comparing means when population variances are heterogeneous.This research was supported by a Social Sciences and Humanities Research Council (SSHRC) grant (# 410-92-0430) to the first author, a Manitoba Health Research Council Scholar Award and a grant from Natural Sciences and Engineering Research Council to the second author, and a SSHRC Doctoral Fellowship (# 752-92-1628) to the third author. The authors would like to express their gratitude to Joanne Keselman and three anonymous reviewers for their many helpful substantive comments on earlier drafts of this paper.     

Brief report: Changing perspectives on aging and intelligence: An empirical update

This study updated the examination of a four-phase, chronological progression model of published research perspectives on aging and intelligence. Phase I research emphasized the inevitable decline of intelligence during adulthood. Phase II research described aging intelligence as a complex multidirectional process with different functions increasing, decreasing, or remaining stable across the life span. Phase III research entailed interventions to enhance aging intelligence. Phase IV research viewed intelligence as continuing to develop and improve throughout adulthood. It was hypothesized that Phase I and Phase II research would decrease during 1986–1995 compared to 1966–1975 and 1976–1985, while Phase III and Phase IV research production would increase in 1986–1995 compared to the previous two decades. A review of 277 articles and 50 dissertations supported the predicted evolution from the unidirectional inevitable decline model toward perspectives describing the plasticity of adult intelligence and the further development and improvement of intelligence across adulthood.