Risk of bias assessment is a mandatory step in any systematic review or meta-analysis, and the summary visualization is one of the most scrutinized figures in your manuscript. The standard tool for generating these charts is robvis, an R package developed by McGuinness and Higgins. The problem: robvis requires R, RStudio, and comfort with command-line package installation.
This guide shows you how to create identical robvis-style charts using our free online tools, step by step, with no installation and no code.
Start with our free Risk of Bias Tool for RCTs and our ROBINS-I Tool for non-randomized studies.
Understanding the Two Chart Types
The traffic light plot shows every included study as a row, with colored circles in each domain column. Green indicates low risk, yellow indicates some concerns, red indicates high risk.
The weighted bar chart aggregates across all studies and shows the percentage in each risk category per domain as horizontal stacked bars. This is the primary figure for manuscripts with many studies.
Both are downloadable as PNG ready for journal submission.
RoB 2 for Randomized Controlled Trials: Step-by-Step
The RoB 2 tool evaluates five domains: randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result.
Step 1: Open the Risk of Bias Tool. Step 2: Add each study and enter its citation. Step 3: Rate each domain as Low, Some concerns, or High. The tool auto-calculates the overall judgment. Step 4: Generate the summary chart. Step 5: Download as PNG.
ROBINS-I for Non-Randomized Studies
ROBINS-I assesses seven domains using a four-level scale: Low, Moderate, Serious, or Critical risk of bias.
Open our ROBINS-I Tool and follow the same sequence: add studies, rate each domain, download the summary chart.
Matching Tool Choice to Study Design
| Study Design | Correct Tool |
|---|---|
| Randomized controlled trial | RoB 2 |
| Cohort study | ROBINS-I |
| Case-control study | ROBINS-I |
| Observational without comparator | Newcastle-Ottawa Scale |
If your review mixes RCTs and observational studies, run both tools separately and present two summary charts.
For observational studies without a comparator group, use our Newcastle-Ottawa Scale tool.
Domain-by-Domain Assessment Tips
Randomization: Check for random sequence generation method and allocation concealment. Deviations: Depends on intention-to-treat vs per-protocol perspective. Missing data: Flag if more than 20% missing without imputation. Measurement: Blinding of assessors matters most for subjective outcomes. Reporting: Compare registered outcomes with reported outcomes.
For overall evidence certainty, complement your risk of bias assessment with our GRADE Evidence Tool.
Key Takeaways
- Use RoB 2 for all randomized controlled trials and the Risk of Bias Tool to generate summary charts online.
- Use ROBINS-I for non-randomized studies and the ROBINS-I Tool for the same chart output.
- Never mix RoB 2 and ROBINS-I judgments in the same summary chart.
- Our tools generate downloadable PNG summary charts that meet journal submission standards.
- Complement bias assessment with GRADE to translate findings into evidence certainty statements.
FAQ
What is the difference between a traffic light plot and a weighted bar chart?
A traffic light plot shows individual study ratings for each domain as colored symbols in a grid. A weighted bar chart aggregates all studies and shows the percentage rated Low, Some concerns, and High per domain as stacked bars.
Can I use NOS instead of ROBINS-I for cohort studies?
Yes. The Newcastle-Ottawa Scale is widely used for cohort and case-control studies. ROBINS-I is more structured and aligns with Cochrane methodology. Our Newcastle-Ottawa Scale tool generates NOS scores.
Do I need two reviewers to complete risk of bias assessments?
Yes. All major reporting guidelines require independent duplicate assessment with disagreements resolved by a third reviewer or consensus discussion.
What should I do with studies rated high risk of bias overall?
Include them in your main analysis and conduct a sensitivity analysis excluding high-risk studies. If the pooled estimate changes substantially, note this in your GRADE assessment.
Is the RoB 2 tool endorsed by Cochrane?
RoB 2 was developed by Cochrane's Risk of Bias Methods Group and is the current Cochrane standard for RCT assessment, replacing the original tool as of 2019.
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