This article covers how to complete a Risk of Bias assessment using RoB 2, Rayyan's tool for randomized controlled trials (RCTs). For an overview of all available tools, how to add articles, and how to select a tool, see How to Use Risk of Bias in Rayyan.
Select RoB 2 as your tool
Before you can start an assessment, select RoB 2 for the article. In the Risk of Bias assessment table, open the Tool dropdown for the article and choose RoB 2 (Randomized trials). This step applies to every tool, not only RoB 2.
Complete an assessment
- Click Start Assessment or double-click the article to open it. The RoB 2 assessment panel appears on the right alongside the article.
- The panel shows five domains (D1–D5), each with a set of signaling questions. Expand a domain to begin.
- Answer each signaling question: Yes, Probably yes, Probably no, No, No information, or N/A.
- Optionally, add a short justification in the text field below each answer. This is not required, but helps transparency and makes your assessment reproducible.
- Once all questions in a domain are answered, the domain judgment appears automatically: Low risk, Some concerns, or High risk.
- Complete all five domains. When the last domain is done, Rayyan calculates and displays the overall risk-of-bias judgment for the article.
- Click Save changes if you're not finished and want to come back later, or Mark as Completed once every domain question is answered.
- Repeat for each article in your assessment.
Best practice Fill in justifications even though they are optional. They make your assessment defensible during peer review and easy to re-check months later when the reasoning behind individual answers is no longer fresh.
The five RoB 2 domains
RoB 2 evaluates each study across five domains, each covering a different type of bias:
| Domain | What it assesses |
|---|---|
| D1 — Randomization process | Was the allocation sequence random and adequately concealed? |
| D2 — Deviations from intended interventions | Did knowledge of the assigned intervention affect what participants or personnel did? |
| D3 — Missing outcome data | Were outcome data available for nearly all participants? Could missing data depend on the true outcome? |
| D4 — Measurement of the outcome | Was the outcome measured appropriately, and were assessors blinded to the intervention? |
| D5 — Selection of the reported result | Was the result selected from multiple analyses in a way that depends on the findings? |
Note The RoB 2 form is fixed, and this is true for MMAT as well. You cannot add, remove, or reword questions. This keeps your assessment aligned with the published methodology and comparable to other RoB 2 reviews. For guidance on answering each signaling question, refer to the official Cochrane RoB 2 crib sheet.
Continue to: MMAT: How to Complete Your Assessment