Meta-analysis

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*If you want to learn what is a meta-analysis...
*If you want to learn what is a meta-analysis...
*If you want to start conducting a meta-analysis...
*If you want to start conducting a meta-analysis...
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==What is a meta-analysis?==
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===Definition===
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===Three Basic Questions===
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A meta-analysis answers three general questions:
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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?
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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.
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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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===Five Basic Steps===
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Define your hypothesis
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Locate the Literature
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Identify and input data
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Cacluate Effect Sizes
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Analyze Variables
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==How do I conduct a meta-analysis?
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===First, choose what statistical approach suits your needs===
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===Second, choose which effect size to calculate?===
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===Third, choose your variables===
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===If you want to follow the Hedges & Olkin approach...===
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===If you want to follow the Rosenthal & Rubin approach...===
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===If you want to follow the Hunter, Schmidt, & Jackson approach...===
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:#There are generally three different statistical approaches to conduct a meta-analysis so first you need to choose which approach best fits your needs.
:#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
Hedges & Olkin Approach – Hedges, 1981; Hedges, 1982; Hedges & Olkin, 1985
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==If you want to follow the Hedges & Olkin approach...==
 
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==If you want to follow the Rosenthal & Rubin approach...==
 
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==If you want to follow the Hunter, Schmidt, & Jackson approach...==
 
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==What are the basic steps in conducting a meta-analysis?==
 
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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?
 

Revision as of 00:27, 18 July 2006

Meta-analysis



Contents

Where should I start?


What is a meta-analysis?

Definition

Three Basic Questions

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?

Five Basic Steps

Define your hypothesis Locate the Literature Identify and input data Cacluate Effect Sizes Analyze Variables


==How do I conduct a meta-analysis?

First, choose what statistical approach suits your needs

Second, choose which effect size to calculate?

Third, choose your variables

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...

  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












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