- done by more than one person
- verification of extracted data
- done by subject experts, methodologists, or both?
- training of coding instructions for forms
- how data will be extracted from multiple reports of the same study
- how disagreements will be handled
5. Selecting studies and collecting data. (2008). In J. Higgins & S. Green (Eds.), Cochrane handbook for systematic reviews of interventions. Chichester, England: Wiley-Blackwell