What Works Clearinghouse: Procedures Handbook, Version 4.1. The WWC systematic review process offers educators and policy-makers a mechanism to assure consistent, objective, and transparent standards and procedures for assessing the impact of practices and interventions. The review procedures handbook includes the following changes: (1) Removal of the “substantively important” designation; (2) Addition of standard error calculations for all effect sizes; (3) Addition of single-case design (SCD) procedures for synthesizing SCD study findings using design-comparable effect sizes; (4) Addition of methods to estimate effects from regression discontinuity designs (RDDs); (5) Clarification of decision rules determining the use of difference-in-difference effect sizes; (6) Synthesis of studies within intervention reports using a fixed-effects model; (7) Modification of the intervention report effectiveness rating; and (8) Levels of evidence in practice guides.
Citation: What Works Clearinghouse: Procedures Handbook, Version 4.1. Princeton, NJ: What Works Clearinghouse https://files.eric.ed.gov/fulltext/ED602035.pdf