Linear regression test of funnel plot asymmetry

Test result: t = -1.72, df = 15, p-value = 0.1055
Bias estimate: -1.2202 (SE = 0.7083)

Details:
- multiplicative residual heterogeneity variance (tau^2 = 2.0982)
- predictor: standard error
- weight:    inverse variance
- reference: Egger et al. (1997), BMJ