Meta analysis techniques are described in detail from their theoretical development through to practical implementation each topic discussed is supported by detailed worked examples a comparison of fixed and random effects approaches is included as well as a discussion of bayesian methods and cumulative meta analysis. Clinical recommendations are often based on evidence derived from meta analysis of randomised controlled trials rcts in your sept 6 editorial1 you ask can meta analyses be trusted there is increasing recognition of the shortcomings of meta analysis and the potential for bias in response to clinically important discrepancies between the results of meta analyses and the results of . Meta analysis of controlled clinical trial chichester john wiley sons ltd abstract over the last twenty years there has been a dramatic upsurge in the application of meta analysis to medical research this has mainly been due to greater emphasis on evidence based medicine and the need for reliable summaries of the vast and expanding volume of clinical research at the same time there . A meta analysis was conducted on controlled clinical trials investigating adaptations of motivational interviewing amis a promising approach to treating problem behaviors amis were equivalent to other active treatments and yielded moderate effects from 25 to 57 compared with no treatment and or placebo for problems involving alcohol drugs and diet and exercise results did not . Meta analysis has evolved as a technique useful for summarizing a large number of clinical trials and for resolving discrepancies raised by these trials there are many similarities between randomized controlled trials and metaanalyses both randomized trials and metaanalyses are designed to answer a scientifically valid question likewise both techniques require that the patients or studies