Systematic reviews are literature reviews of primary research in health care and policy. A systematic review addresses a clearly formulated question. To answer the question a search is done to collate all the existing primary research on the topic. The information from the primary research is then analyzed by meta-analysis, which uses statistical methods to combine the information from separate but similar studies and derive conclusions. A systematic review of randomized controlled trials informs evidence-based medicine, an approach to medical practice intended to optimize decision-making by emphasizing the use of evidence from well-designed and well-conducted research.