Box 2 Study internal validity assessment
Internal validity criteria | Type of bias addressed |
|---|---|
Was the study free of any baseline factors that may be associated with both the intervention and outcome of interest (or different participant groups if non-comparative)? | Confounders at baseline/selection bias |
Was the study free of any external events or factors during the study that could influence the outcome of interest? | Confounding |
Were the intervention (and comparator, if present) clearly defined, at an appropriate temporal and spatial scale, and adhered to as intended? | Appropriate intervention/comparator |
Was an appropriate method used to measure the outcome across all study groups? | Detection bias |
Were all data reported, or was the study clear of any systematic differences between study groups in the number of missing data? | Attrition bias |
Were all outcome measurements reported appropriately? | Outcome reporting bias |