Risk of Bias 2 assessment tool

Joshua Yu March 26, 2025 #tools #research
Quick start

Tool is derived directly from the Cochrane Risk of Bias assessment tool, licensed under CC BY-NC-ND 4.0. Higgins (2019).



See here for an abridged guide to the tool. Chose domain 2a or 2b, but not both.

Click the overall button to copy a summary of the results. Unless you click the above button or clear your cache, your selections/text will be saved.

D1 D2a D2b D3 D4 D5
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Domain 1: Risk of bias arising from the randomization process

Question Answer Details
1.1: Was the allocation sequence random?
1.2: Was the allocation sequence concealed until participants were enrolled and assigned to interventions?
1.3: Did baseline differences between intervention groups suggest a problem with the randomization process?
Risk of bias judgement

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Domain 2a: Risk of bias due to deviations from the intended interventions (effect of assignment to intervention)

Use this if you want to assess the effect of assignment to the interventions at baseline, regardless of whether the interventions are received as intended (the ‘intention-to-treat effect’).
Question Answer Details
2.1: Were participants aware of their assigned intervention during the trial?
2.2: Were carers and people delivering the interventions aware of participants' assigned interventions?
2.3: If Y/PY/NI to 2.1 or 2.2: Were there deviations from the intended intervention that arose because of the trial context?
2.4: If Y/PY to 2.3: Were these deviations likely to have affected the outcome?
2.5: If Y/PY/NI to 2.4: Were these deviations from intended intervention balanced between groups?
2.6: Was an appropriate analysis used to estimate the effect of assignment to intervention?
2.7: If N/PN/NI to 2.6: Was there potential for a substantial impact (on the result) of the failure to analyse participants in the group to which they were randomized?
Risk of bias judgement

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Domain 2b: Risk of bias due to deviations from the intended interventions (effect of adhering to intervention)

This variant of domain 2 should be used if: you want to assess the effect of adhering to the interventions as specified in the trial protocol (the ‘per-protocol effect’)
Question Answer Details
2b.1: Were participants aware of their assigned intervention during the trial?
2b.2: Were carers and people delivering the interventions aware of participants' assigned intervention during the trial?
2b.3: If Y/PY/NI to 2.1 or 2.2: Were important non-protocol interventions balanced across intervention groups?
Answer Y if not applicable.
2b.4: Were there failures in implementing the intervention that could have affected the outcome?
Answer N if not applicable.
2b.5: Was there non-adherence to the assigned intervention regimen that could have affected participants’ outcomes?
Answer N if not applicable.
2b.6: If N/PN/NI to 2.3, or Y/PY/NI to 2.4 or 2.5: Was an appropriate analysis used to estimate the effect of adhering to the intervention?
Risk of bias judgement

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Domain 3: Missing outcome data

Question Answer Details
3.1: Were data for this outcome available for all, or nearly all, participants randomized?
3.2: If N/PN/NI to 3.1: Is there evidence that the result was not biased by missing outcome data?
3.3: If N/PN to 3.2: Could missingness in the outcome depend on its true value?
3.4: If Y/PY/NI to 3.3: Is it likely that missingness in the outcome depended on its true value?
Risk of bias judgement

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Domain 4: Risk of bias in measurement of the outcome

Question Answer Details
4.1: Was the method of measuring the outcome inappropriate?
4.2: Could measurement or ascertainment of the outcome have differed between intervention groups?
4.3: If N/PN/NI to 4.1 and 4.2: Were outcome assessors aware of the intervention received by study participants?
4.4: If Y/PY/NI to 4.3: Could assessment of the outcome have been influenced by knowledge of intervention received?
4.5: If Y/PY/NI to 4.4: Is it likely that assessment of the outcome was influenced by knowledge of intervention received?
Risk of bias judgement

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Domain 5: Risk of bias in selection of the reported result

Question Answer Details
5.1: Were the data that produced this result analysed in accordance with a pre-specified analysis plan that was finalized before unblinded outcome data were available for analysis?
5.2: Is the numerical result being assessed likely to have been selected, on the basis of the results, from multiple eligible outcome measurements (e.g. scales, definitions, time points) within the outcome domain?
5.3: Is the numerical result being assessed likely to have been selected, on the basis of the results, from multiple eligible analyses of the data?
Risk of bias judgement

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