Figure 2

Funnel plot of the odds-ratio against the precision of the estimates. Points to the right of the dashed line are significant at the 5% level. The apex of the funnel gives the point estimate. Points outside the funnel differ from the point estimate at the 5% level and suggest heterogeneity in the estimates. If there is no bias in the selection of studies for publication, the points should be evenly scattered to the left and right. Squares represent the three studies with largest standard error that were excluded in the category "Excluding three smallest studies" in table 2 (Mori et al 1992, Spletter 2000, and Riekstina et al 2005). The two filled circles that are outside the funnel represent the two additional studies that were excluded in the category "Excluding three smallest and Brown I and Kim" in table 2