There are a variety of different procedures for conducting a meta-analysis
involving the accumulation of correlations (r), standardized differences
between mean scores (d), p values, or Z-scores (Glass,
1976, 1977; Hunter et al.,1982; Hunter and Schmidt, 1990; Rosenthal, 1991;
Smith and Glass, 1977;
Smith, Glass and Miller, 1980; Wolf, 1986).
Schmidt, Hunter, and their colleagues (Schmidt and Hunter, 1977; Hunter, et.
al., 1982; Hunter and Schmidt, 1990) developed one method of meta-analysis
that does not rely on the combination of Z-scores or probability
values as the common metric. This procedure uses either r or d as
the combinatorial statistic. It progressively corrects the mean r or d and
their obtained variances for sampling error and then measurement error and