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. 2021 Jul 26;129(7):076003. doi: 10.1289/EHP8421

Table 2.

Risk of bias analysis: domains of bias and questions.

Domain of bias Risk of bias question
Selection bias 1. Was administered dose or exposure level adequately randomized?
Selection bias 2. Was allocation to study groups adequately concealed?
Performance bias 3. Were experimental conditions identical across study groups?*
Performance bias 4. Were the research personnel blinded to the study group during the study?
Attrition bias 5. Were outcome data incomplete due to attrition or exclusion from analysis?
Detection bias 6. Can we be confident in the exposure characterization?*
Detection bias 7. Can we be confident in the outcome assessment?*
Selective reporting bias 8. Were all measured outcomes reported?
Other 9. Were there any other potential threats to internal validity?

Note: Key elements considered for the tiered classification are marked by an asterisk (*).