Begg's funnel plot for publication bias in meta-analysis of premature birth and breast cancer risk. Premature birth (gestational age ≤36 weeks) was compared with gestational age ≥37 weeks. Egger test, P = 0.03; Begg test, P = 0.11. rr, relative risk; s.e., standard error.
Park et al. Breast Cancer Research 2008 10:R8 doi:10.1186/bcr1850