Linear regression test of funnel plot asymmetry

Test result: t = -0.20, df = 17, p-value = 0.8449
Bias estimate: -0.1627 (SE = 0.8192)

Details:
- multiplicative residual heterogeneity variance (tau^2 = 5.1376)
- predictor: standard error
- weight:    inverse variance
- reference: Egger et al. (1997), BMJ