Y học - Chapter 11: Meta-Analysis

Chapter 11Meta-AnalysisMeta-analysisQuantitative means of reanalyzing the results from a large number of research studies in an attempt to synthesize findingsMore than merely a review of related literatureRelatively new approach in HHP researchEffect SizeBasic statistic used in meta-analysisConverts results from different studies to a common metric so that comparisons can be madeUsed to estimate meaningfulness of an outcome (i.e., practical significance)Not influenced by sample sizeExample Size FormulaES = (Me – Mc)/ScFormula for estimating ES for difference between experimental and control group. Where Me is the mean of the experimental group, Mc is the mean of the control group, and Sc is the standard deviation of the control group.Note: There are numerous formulas that can be used to calculate ES.Interpretation of ES .80 largeSource: Cohen (1988)Meta -AnalysisIn meta-analysis, each research study contributes a data point to the subsequent analysis, much like an individual participant in a descriptive or experimental research studySteps in Meta-AnalysisCompile referencesThere must be a substantial number of research studies available on a topicRequires means, standard deviations, correlations, etc. be publishedDetermine inclusive criteriaE.g., published in last 10 years or N > 30Review each studyRecord information needed to calculate ES from each studyIdentify and code moderator variables, if anySteps in Meta-Analysis cont.Decide which studies to useDo the meta-analysisCalculate the effect size for each studyGenerate summary statistics for effect sizesExamine according to moderator variablesInterpret resultsReport the resultsCriticism of Meta-AnalysisNot the ultimate answerDoes not differentiate in quality of studiesCombines unlike studies with too much variability (i.e., mixing apples and oranges)Inappropriate coding of variables