Copyright © Allyn & Bacon (2010) Meta-Analysis Graziano and Raulin Research Methods: Appendix H This multimedia product and its contents are protected

Copyright © Allyn & Bacon (2010)Copyright © Allyn & Bacon (2010)

Meta-AnalysisMeta-Analysis

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Meta-AnalysisMeta-Analysis

A statistical way to combine A statistical way to combine several studies on a single topicseveral studies on a single topic

InvolvesInvolves– Computing an effect size for each Computing an effect size for each

studystudy– Computing a weighted effect size for Computing a weighted effect size for

the series of studiesthe series of studies Advances scientific understandingAdvances scientific understanding


Meta-analysisMeta-analysis

Science builds on its cumulative Science builds on its cumulative knowledgeknowledge

But statistical procedures tend to But statistical procedures tend to discount information from a study discount information from a study if the findings fall short of if the findings fall short of statistical significancestatistical significance

Meta-analysis combines both Meta-analysis combines both significant and non-significant significant and non-significant findingsfindings

Type II ErrorType II Error

Refers to failing to reject a null Refers to failing to reject a null hypothesis that should have been hypothesis that should have been rejectedrejected– Some non-significant statistical tests are Some non-significant statistical tests are

type II errors (due to insufficient power)type II errors (due to insufficient power)– Normally, these non-significant studies are Normally, these non-significant studies are

ignored (that is, never published)ignored (that is, never published) Meta-analysis deals with Type II errors Meta-analysis deals with Type II errors

by including these non-significant by including these non-significant findings in the analysisfindings in the analysis



SummarySummary

Meta-analysis statistically combines Meta-analysis statistically combines the results of studies of the same the results of studies of the same phenomenaphenomena

An alternative to the traditional An alternative to the traditional literature reviewliterature review

By objectively summing the effects By objectively summing the effects from all studies, it goes beyond the from all studies, it goes beyond the question of statistical significancequestion of statistical significance

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Copyright © Allyn & Bacon (2010) Meta-Analysis Graziano and Raulin Research Methods: Appendix H This multimedia product and its contents are protected