Yet another reason to synthesise the result of different studies of a given intervention is to learn whether findings are consistent across multiple studies. Light and Pillemer (1984) have written that 'disagreements among findings are valuable (that and) conflicts can teach us a lot'. This is because we are able to see in what settings a particular social policy might succeed, under what circumstances an educational programme might work best, or what does of a drug is most effective. A good research synthesis frequently highlights weaknesses in the evidence and argues for further research. What should service users, policymakers, and others decide in the absence of evidence?