Meta-analysis

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==Where should I start?==
==Where should I start?==
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If you want to learn <u>what is a meta-analysis</u>...
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#For the '''basics''' behind meta-analyses see below where we lay out
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<TABLE BORDER=1 CELLSPACING=0 CELLPADDING=5>
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::*the [[#Definition | definition]] of a meta-anlaysis,
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<TR>
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::*the [[#Three Basic Questions | three basic questions]] answered by a meta-analysis,
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<TD valign=top width=370>
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::*the [[#Five Basic Steps | the five steps]] involved in a meta-analysis,
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If you want to learn '''what is a meta-analysis'''...
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#For more '''in-depth''' discussion and explanations, we recommend...
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<ol>
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::start first with  
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<li>For the <u>basics</u>, see below where we lay out:</li>
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*the [[#Definition | definition]] of a meta-anlaysis,
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*the [[#Three Basic Questions | three basic questions]] answered by a meta,
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*the [[#Five Basic Steps | the five steps]] involved in a meta-analysis,
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<li>For more <u>in-depth</u> discussion and explanations, we recommend...</li>
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*start first with
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*
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*
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</ol>
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</TD>
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<TD valign=top width=370>
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If you want to learn '''how to start conducting a meta-analysis'''...
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<ol>
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<li>For the <u>basics</u>, see below were we lay out:</li>
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*how to [[#First, choose what statistical approach suits your needs | choose a statistical approach]]
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*how to [[#Second, choose which effect size to calculate? | choose which effect size to calculate]]
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*how to [[#Third, choose your statistical software | choose your statistical software]]
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<li>For more <u>in-depth</u> discussion and explanations, we recommend...</li>
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*start first with '''[[Johnson, Mullen, & Salas, 1995]]''' which provides a statistical comparision of the three major meta-analytic approaches using actual datasets, as well as the staistical forumulas for each approach and the methodological differences between each approach.
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*
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</ol>
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</TD>
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</TABLE>
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If you want to learn <u> how to start conducting a meta-analysis.</u>..
 
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:*For the '''basics''' behind conducting a meta-analysis see below were we lay out:
 
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::how to [[#First, choose what statistical approach suits your needs | choose a statistical approach]] to conducting a meta-analysis,
 
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::the [[
 
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::the [[
 
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:*For more '''in-depth''' discussion and explanations, we recommend...
 
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::start first with '''[[Johnson, Mullen, & Salas, 1995]]''' which provides a statistical comparision of the three major meta-analytic approaches using actual datasets, as well as the staistical forumulas for each approach and the methodological differences between each approach.
 
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===Second, choose which effect size to calculate?===
===Second, choose which effect size to calculate?===
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===Third, choose your variables===
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===Third, choose your statistical software===
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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 02:12, 18 July 2006

Have you ever wanted to learn about meta-analysis or conduct a meta-analysis but didn't know where to start? This webpage is devoted to providing


Contents

Where should I start?

If you want to learn what is a meta-analysis...

  1. For the basics, see below where we lay out:

  2. For more in-depth discussion and explanations, we recommend...
    • start first with

If you want to learn how to start conducting a meta-analysis...

  1. For the basics, see below were we lay out:

  2. For more in-depth discussion and explanations, we recommend...
    • start first with (Johnson, Mullen, & Salas, 1995) which provides a statistical comparision of the three major meta-analytic approaches using actual datasets, as well as the staistical forumulas for each approach and the methodological differences between each approach.



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 (variability), then we look for moderating variables that explain the variability. In other words, does the effect of X on Y differ with moderator variables?

Five Basic Steps

There are generally five separate steps in conducting a meta-analysis:
  1. Define your hypothesis
  2. Locate the Literature
  3. Identify and input data
  4. Cacluate Effect Sizes
  5. Analyze Variables


How do I conduct a meta-analysis?

First, choose what statistical approach suits 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. For an excellent detailed comparison of these three approaches, see (Johnson, Mullen, & Salas, 1995) (Comparison of Three Major Meta-Analytic Approaches. Journal of Applied Psychology, 80, 94-106). Some basic information from that article is posted below to get you started:
  1. Hedges & Olkin Approach – see (Hedges, 1981); (Hedges, 1982); (Hedges & Olkin, 1985)
  2. Rosenthal & Rubin Approach – see (Rosenthal, 1991); (Rosenthal & Rubin, 1978); (Rosenthal & Rubin, 1988)
  3. Hunter, Schmidt, & Jackson - see (Hunter, Schmidt, & Jackson, 1982); (Hunter & Schmidt, 1990)
Table1JMS2.gif

Second, choose which effect size to calculate?

Third, choose your statistical software

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...

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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