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Risk of bias requirements
When a study is entered into the HAWC database for use in an assessment, risk of bias metrics can be entered for a metric of bias for each study. Risk of Bias metrics are organized by domain. The following questions are required for evaluation for this assessment.
Requirements by Study Type
| Domain | Metric | Bioassay | Epidemiology | In Vitro |
|---|---|---|---|---|
| Selection | Did selection of study participants result in appropriate comparison groups? | - | ✔ | ✔ |
| Selection | Was administered dose or exposure level adequately randomized? | ✔ | - | ✔ |
| Selection | Was allocation to study groups adequately concealed? | ✔ | - | ✔ |
| Confounding | Did the study design or analysis account for important confounding and modifying variables? | - | ✔ | ✔ |
| Performance | Were experimental conditions identical across study groups? | ✔ | - | ✔ |
| Performance | Were the research personnel and human subjects blinded to the study group during the study? | ✔ | ✔ | ✔ |
| Attrition | Were outcome data incomplete due to attrition or exclusion from analysis? | ✔ | ✔ | ✔ |
| Detection | Can we be confident in the exposure characterization? | ✔ | ✔ | ✔ |
| Detection | Can we be confident in the outcome assessment? | ✔ | ✔ | ✔ |
| Selective Reporting | Were all measured outcomes reported? | ✔ | ✔ | ✔ |
| Other | Were there any other potential threats to internal validity? | ✔ | ✔ | ✔ |
| Other | Control for litter effects | ✔ | - | ✔ |
Selection
Was administered dose or exposure level adequately randomized?
Randomization requires that each human subject or animal had an equal chance of being assigned to any study group including controls (e.g., use of random number table or computer generated randomization).
Was allocation to study groups adequately concealed?
Allocation concealment requires that research personnel do not know which administered dose or exposure level is assigned at the start of a study. Human studies also require that allocation be concealed from human subjects prior to entering the study.
Note:
- a question under performance bias addresses blinding of personnel and human subjects to treatment during the study;
- a question under detection bias addresses blinding of outcome assessors.
Performance
Were experimental conditions identical across study groups?
Were the research personnel and human subjects blinded to the study group during the study?
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition
Were outcome data incomplete due to attrition or exclusion from analysis?
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection
Can we be confident in the exposure characterization?
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Selective Reporting
Were all measured outcomes reported?
Other
Were there any other potential threats to internal validity?
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include appropriateness of statistical methods, adherence to the study-protocol, etc.
Control for litter effects
Text to be added
Selection
Did selection of study participants result in appropriate comparison groups?
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Confounding
Did the study design or analysis account for important confounding and modifying variables?
Performance
Were the research personnel and human subjects blinded to the study group during the study?
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition
Were outcome data incomplete due to attrition or exclusion from analysis?
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection
Can we be confident in the exposure characterization?
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Selective Reporting
Were all measured outcomes reported?
Other
Were there any other potential threats to internal validity?
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include appropriateness of statistical methods, adherence to the study-protocol, etc.
Selection
Did selection of study participants result in appropriate comparison groups?
Comparison group appropriateness refers to having similar baseline characteristics between the groups aside from the exposures and outcomes under study.
Was administered dose or exposure level adequately randomized?
Randomization requires that each human subject or animal had an equal chance of being assigned to any study group including controls (e.g., use of random number table or computer generated randomization).
Was allocation to study groups adequately concealed?
Allocation concealment requires that research personnel do not know which administered dose or exposure level is assigned at the start of a study. Human studies also require that allocation be concealed from human subjects prior to entering the study.
Note:
- a question under performance bias addresses blinding of personnel and human subjects to treatment during the study;
- a question under detection bias addresses blinding of outcome assessors.
Confounding
Did the study design or analysis account for important confounding and modifying variables?
Performance
Were experimental conditions identical across study groups?
Were the research personnel and human subjects blinded to the study group during the study?
Blinding requires that study scientists do not know which administered dose or exposure level the human subject or animal is being given (i.e., study group). Human studies also require blinding of the human subjects when possible.
Attrition
Were outcome data incomplete due to attrition or exclusion from analysis?
Attrition rates are required to be similar and uniformly low across groups with respect to withdrawal or exclusion from analysis
Detection
Can we be confident in the exposure characterization?
Confidence requires valid, reliable, and sensitive methods to measure exposure applied consistently across groups.
Can we be confident in the outcome assessment?
Confidence requires valid, reliable, and sensitive methods to assess the outcome and the methods should be applied consistently across groups.
Selective Reporting
Were all measured outcomes reported?
Other
Were there any other potential threats to internal validity?
On a project specific basis, additional questions for other potential threats to internal validity can be added and applied to study designs as appropriate.
Examples may include appropriateness of statistical methods, adherence to the study-protocol, etc.
Control for litter effects
Text to be added