Linear regression test of funnel plot asymmetry

Test result: t = -0.85, df = 15, p-value = 0.4061
Bias estimate: -0.7578 (SE = 0.8864)

Details:
- multiplicative residual heterogeneity variance (tau^2 = 1.3275)
- predictor: standard error
- weight:    inverse variance
- reference: Egger et al. (1997), BMJ