Meta-analysis

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==If you want to follow the Hedges & Olkin approach...==
==If you want to follow the Hedges & Olkin approach...==

Revision as of 00:17, 18 July 2006

Meta-analysis



Contents

Where should I start?

  1. There are generally three different statistical approaches to conduct a meta-analysis so first you need to choose which approach best fits your needs.

Hedges & Olkin Approach – Hedges, 1981; Hedges, 1982; Hedges & Olkin, 1985

Rosenthal & Rubin Approach – Rosenthal, 1991; Rosenthal & Rubin, 1978; Rosenthal & Rubin, 1988

Hunter, Schmidt, & - Hunter, Jackson, 1982; Hunter & Schmidt, 1990

File:Table1.gif

Just as an individual study collects data from many individuals (data points) that is statistically summarized to answer the question of interest, a meta-anlay



If you want to follow the Hedges & Olkin approach...

If you want to follow the Rosenthal & Rubin approach...

If you want to follow the Hunter, Schmidt, & Jackson approach...

What are the basic steps in conducting a meta-analysis?

A meta-analysis answers three general questions: 1. Central tendency – The central purpose of a meta-analysis is to test the relationship between two variables such that X causes Y. Central tendency refers to identifying whether X affects Y via statistically summarizing signficance levels, effect sizes, and/or confidence intervals. You are trying to answer whether X affects Y, is the effect significant, and how strong is that effect? 2. Variability – There is always going to be some degree of variation between the outcomes of the individual studies that compose the meta-analysis. The question is whether the degree of variablity is signficantly different than what we would expect by chance alone. If so, then its called heterogeneity. 3. Prediction – If there is heterogeneity (variablitiy), then we look for moderating variables that explain the variablitty? In other words, does the effect of X on Y differ with moderator variables?










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