Meta-analytic methods, the Rorschach, and the MMPI.

In response to concerns described by H. N. Garb, J. M. Wood, M. T. Nezworski, W. M. Grove, and W. J. Stejskal (2001), the authors present the weighted and unweighted means and medians of the effect sizes obtained by J. B. Hiller, R. Rosenthal, R. F. Bornstein, D. T. R. Berry, and S. Brunell-Neuleib (1999). These indices of central tendency are presented separately for Minnesota Multiphasic Personality Inventory (MMPI) and Rorschach effect sizes, both for all the studies in the meta-analysis and for a 10% trimmed sample designed to obtain more robust estimates of central tendency. The variability of these 4 indices is noticeably greater for the MMPI than for the Rorschach. Meta-analysts must compute, compare, and evaluate a variety of indices of central tendency, and they must examine the effects of moderator variables. The authors also comment briefly on the use of phi versus kappa, combining correlated effect sizes and possible hindsight biases.