  Research on methods of meta-analysis (the synthesis of related study results)
has dealt with many simple study indices, but less attention has been paid to
the issue of summarizing regression slopes. In part this is because of the many
complications that arise when real sets of regression models are accumulated.
We outline the complexities involved in synthesizing slopes, describe existing
methods of analysis and present a multivariate generalized least squares
approach to the synthesis of regression slopes.
