Risk of bias assessment helps to establish transparency of evidence synthesis results and findings. A risk of bias assessment and/or a quality appraisal assessment are often performed for each included study in a review. Systematic reviews strive to eliminate bias in their findings. Individual studies that are included in a synthesis may include biases in their results or conclusions, for example design flaws that raise questions about validity of findings or an overestimate of intervention effect.
Risk of bias assessments can be represented in table format in an evidence synthesis, showing each included study and how strong it is across several quality criteria for that particular study type for example:
If a high proportion of studies are assessed with a high risk of bias, caution should be used when interpreting results for your evidence synthesis. More information can be found in Chapter 8 of the Cochrane Handbook.