About this example
Not every scattered funnel means publication bias. The 13 BCG vaccine trials (Colditz et al., JAMA 1994) spread far beyond the pseudo confidence limits on both sides, because the true effect differs between trials (I² above 90%), partly with latitude.
Egger’s test (P ≈ 0.19) and Begg’s test (P ≈ 0.95) find no asymmetry, and trim and fill imputes a single study. When heterogeneity is this large, funnel plot tests are hard to interpret, which is why Sterne et al. (BMJ 2011) advise exploring heterogeneity first.
The data
| Study | Events T | Total T | Events C | Total C |
|---|---|---|---|---|
| Aronson 1948 | 4 | 123 | 11 | 139 |
| Ferguson & Simes 1949 | 6 | 306 | 29 | 303 |
| Rosenthal et al 1960 | 3 | 231 | 11 | 220 |
| Hart & Sutherland 1977 | 62 | 13598 | 248 | 12867 |
| Frimodt-Moller et al 1973 | 33 | 5069 | 47 | 5808 |
| Stein & Aronson 1953 | 180 | 1541 | 372 | 1451 |
| Vandiviere et al 1973 | 8 | 2545 | 10 | 629 |
| TPT Madras 1980 | 505 | 88391 | 499 | 88391 |
| Coetzee & Berjak 1968 | 29 | 7499 | 45 | 7277 |
| Rosenthal et al 1961 | 17 | 1716 | 65 | 1665 |
| Comstock et al 1974 | 186 | 50634 | 141 | 27338 |
| Comstock & Webster 1969 | 5 | 2498 | 3 | 2341 |
| Comstock et al 1976 | 27 | 16913 | 29 | 17854 |
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