TABLE 2

A Classification Scheme for Bias (Based on Table 8.4.1 in Cochrane Handbook for Systematic Reviews of Interventions10)

Type of biasDescriptionRelevant Domains in the Cochrane Risk of Bias Tool
Selection biasSystematic differences between the baseline characteristics of the groupsSequence generation; allocation concealment
Performance biasSystematic differences between the groups in the care that is provided or in exposure to factors other than the interventions of interestBlinding; other sources of bias
Attrition biasSystematic differences between groups in withdrawals from the studyIncomplete outcome data; blinding
Detection biasSystematic differences between groups in how outcomes are measuredBlinding; other sources of bias
Reporting biasSystematic differences between reported and unreported findingsSelective outcome reporting