Generalised interval estimation in the random effects meta regression model

The explanation of heterogeneity when combining different studies is an important issue in meta analysis. Besides including a heterogeneity parameter in the analysis, it is also important to understand the possible causes of heterogeneity. A possibility is to incorporate study-specific covariates in the model that account for between-trial variability. This leads to the random effects meta regression model. Commonly used methods for constructing confidence intervals for the regression coefficients are examined and two new methods based on generalised inference principles are proposed. The different methods are compared by an extensive simulation study with respect to coverage probability and average length.