In order to account for the possibility that results of the meta-analysis were affected by publication bias, we calculated the number of unpublished studies that would have to exist to change the outcome of the Liptak-Stouffer test from significant to non-significant (Fail-safe N)67. The ratio between the Fail-safe N and the number of studies actually published gives an estimate for the likelihood that the significant meta-analytical result is due to publication bias.
