From the abstract: "A general approach for conducting power analysis in two- and three-level hierarchical linear models (HLMs) is described. The method can be used to perform power analysis to detect fixed effects at any level of a HLM with dichotomous or continuous covariates. It can easily be extended to perform power analysis for functions of parameters. Important steps  in  the  derivation  of  this  approach  are  illustrated  and  numerical  examples  are provided. Sample code implementing this approach is provided using the free program R."