Trim and Fill: A Simple Funnel-Plot–Based Method of Testing and Adjusting for Publication Bias in Meta-Analysis
Article first published online: 24 MAY 2004
Volume 56, Issue 2, pages 455–463, June 2000
How to Cite
Duval, S. and Tweedie, R. (2000), Trim and Fill: A Simple Funnel-Plot–Based Method of Testing and Adjusting for Publication Bias in Meta-Analysis. Biometrics, 56: 455–463. doi: 10.1111/j.0006-341X.2000.00455.x
- Issue published online: 24 MAY 2004
- Article first published online: 24 MAY 2004
- Received October 1998. Revised June 1999. Accepted July 1999.
- Data augmentation;
- File drawer problem;
- Funnel plots;
- Missing studies;
- Publication bias
Summary. We study recently developed nonparametric methods for estimating the number of missing studies that might exist in a meta-analysis and the effect that these studies might have had on its outcome. These are simple rank-based data augmentation techniques, which formalize the use of funnel plots. We show that they provide effective and relatively powerful tests for evaluating the existence of such publication bias. After adjusting for missing studies, we find that the point estimate of the overall effect size is approximately correct and coverage of the effect size confidence intervals is substantially improved, in many cases recovering the nominal confidence levels entirely. We illustrate the trim and fill method on existing meta-analyses of studies in clinical trials and psychometrics.