A meta-analysis of outcome studies comparing bona fide psychotherapies: Empiricially, "all must have prizes."

@article{Wampold1997AMO,
  title={A meta-analysis of outcome studies comparing bona fide psychotherapies: Empiricially, "all must have prizes."},
  author={Bruce E. Wampold and Gregory W. Mondin and Marcia Moody and Frederick A. Stich and Kurt P Benson and Hyun-nie Ahn},
  journal={Psychological Bulletin},
  year={1997},
  volume={122},
  pages={203-215}
}
This recta-analysis tested the Dodo bird conjecture, which states that when psychotherapies intended to be therapeutic are compared, the true differences among all such treatments are 0. Based on comparisons between treatments culled from 6 journals, it was found that the effect sizes were homogeneously distributed about 0, as was expected under the Dodo bird conjecture, and that under the most liberal assumptions, the upper bound of the true effect was about .20. Moreover, the effect sizes (a… 

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