Objectives: To provide an introduction to the different forms of reporting biases and the methods that might be used to detect these biases.

Summary: The results of a meta-analysis can be distorted if bias has been introduced into the review process when component studies are being located and selected. Accordingly, investigation for the presence, degree, and nature of bias is recommended as a routine part of the systematic review process. The Cochrane Reporting Bias Methods Group draws together researchers interested in this field. The workshop will largely draw upon the work of members of this group. We will discuss potential biases that might be introduced into reviews, with an emphasis on reporting biases. Particular attention will be paid to the effects of trial quality, publication bias (the publication or non-publication of research findings, depending on the nature and direction of the results), and other reporting biases including outcome selection biases. We will demonstrate and discuss graphical and statistical methods that can be used to detect or investigate bias. These include the funnel plot, 'trim and fill' tests for funnel plot asymmetry, and meta-regression. The workshop will consist of PowerPoint presentations, and discussions with and among participants.

Level of knowledge required to attend: basic.