(3) To answer questions not raised by individual studies. (4) To resolve controversies that arise from studies with conflicting results or generate new hypotheses for future studies. Well- known problems and limitations of a meta- analysis include failure to identify all relevant studies, whether or not to include unpublished data, variable quality of included trials, inconclusive systematic reviews, opposite conclusions, and discrepancies between the results of a meta- analysis and a large RCT (discussed in detail elsewhere) [8, 9].