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Meta-analysis

Traditional approaches to research synthesis. Simple Adhoc narrative assessment of Literature.Fails to accumulate and integrate findingssubject to biasBox Scoresrelatively insensitive for small studiespower decreases as n increasesVoting methods/Contingency TablesContingency table approach

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Meta-analysis

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    1. Meta-analysis The Objective Review of Research

    2. Traditional approaches to research synthesis Simple Adhoc narrative assessment of Literature. Fails to accumulate and integrate findings subject to bias Box Scores relatively insensitive for small studies power decreases as n increases Voting methods/Contingency Tables Contingency table approach tends to be biased, incomplete. As n increases chance of detecting real effects decreases.

    3. Meta-analytic approach Need for an explicit, unambiguous, systematic approach that would produce objective consistent outcomes Glass (1977) suggested; That data from studies could be treated as the experimental unit in a mega study. That effect sizes, or correlations could be used as the data in these studies.

    4. Definitions Meta -analysis - The analysis of analyses. Effect size - a measure of the magnitude of a research outcome. Correlation - a measure of the magnitude and direction of association between variables. Group differentiation - The ratio of positive outcomes to negative outcomes.

    5. Glass’s Approach to meta analysis Standard mean difference Correlation Coefficient

    6. Isn’t this too easy? Criticisms of Meta-analysis. Four criticisms have been made of meta-analysis. Logical conclusions cannot be drawn from hetrogenous studies (Mega-silliness). Poorly designed studies contaminate meta-studies. Published research is biased in favour of significant outcomes. Multiple results from the same study which bias the result to positive outcomes.

    7. Responses to the criticisms Heterogeneity can be controlled for by recording sources of heterogeneity, and treating statistically (see Wolf) Heterogeneity of quality can be controlled by rating studies quality, and weighting results or excluding poor studies (QSRF questionnaire). Approaches to the file draw problem include using funnel diagrams to decide if you have a problem, failsafe N to calculate the minimum number of studies required, and seeking unpublished papers. Similar approaches to 1 and 2 (see Wolf)

    8. Combined tests in meta analysis. Fisher’s combined test Winer’s combined test Stouffer combined test

    10. Combined test result

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