Once you know how you are going to do your validity assessment, you can design this component of your data collection form. If you are assessing whether a study met certain key criteria you need to list them, using either a checklist or categories of the 'Risk of bias' table as outlined in Section 8.5 of the Cochrane Handbook for Systematic Reviews of Interventions. Some examples of criteria you may wish to include are:
- Selection Bias (Was the study randomised? Was allocation concealment adequate?)
- Performance Bias (Were participants and care providers blind to the intervention? Were there any co-interventions?)
- Attrition Bias (Were all participants randomised accounted for in the anaysis? Were any withdrawers described?)
- Detection Bias (Was there a blinded assessment of outcome)
- Analysis (Was the analysis appropriate?)
Design your form now, bearing in mind all the aspects of validity assessment you wish to use. You will need to test out how your form works, but we will discuss that later.