Assessing risk of bias in randomized trials: RoB 2

Core Methods Workshop

Workshop category: 

  • Investigating bias
Date and Location


Tuesday 22 October 2019 - 14:00 to 15:30


Contact persons and facilitators

Contact person:


Savovic J1, Higgins J1, Sterne J1, Page M2
1 University of Bristol, UK
2 Monash University, Australia


Target audience

Target audience: 

Systematic review authors, trialists and people from other disciplines with an interest in how bias can arise in randomized controlled trials

Level of difficulty: 

Type of workshop

Type of workshop : 



Background: randomized controlled trials (RCTs) provide evidence about the effects of healthcare interventions. However, trial results can be undermined by flaws in design, conduct, analyses and selective reporting. Therefore, review authors should systematically take into account risk of bias in results of included studies when interpreting the results of their review. The revised 'Risk of bias' tool (RoB 2) is a major update to the Cochrane tool for assessing risk of bias in RCTs (RoB 1), which was introduced in 2008 and revised in 2011.

Objectives: to explain the key concepts that underpin RoB 2 and gain experience in using it to assess risk of bias in RCTs.

Description: we will present the key features of RoB 2:
- specification of the result to be assessed;
- specification of the effect of interest (that of assignment to intervention, or adhering to intervention);
- five consolidated bias domains;
- signalling questions that lead to algorithm-guided 'Risk of bias' judgments within bias domains;
- derivation of an overall 'Risk of bias' judgment for the assessed result.

We will describe the five domains of bias included within RoB 2: bias arising from the randomization process, bias due to deviations from intended interventions, bias due to missing outcome data, bias in the measurement of the outcome, and bias in the selection of the reported result. We will also describe changes, based on user feedback and developments in the field, made to the tool since its initial release in 2016.

A worked example will be used to provide hands-on training and facilitate discussion. Participants will have the option to complete their assessments in a semi-automated Excel template, and are encouraged to bring their own portable device to access detailed guidance from the internet ( Please note that the facilitators are unable to provide printed copies of the guidance document.