Metaanalysis
From PsychWiki  A Collaborative Psychology Wiki
Line 34:  Line 34:  
<ol>  <ol>  
<li>For the <u>basics</u>, see below were we lay out:</li>  <li>For the <u>basics</u>, see below were we lay out:</li>  
  *how to [[#First, choose  +  *how to [[#First, choose which statistical approach suits your needs  choose a statistical approach]] 
*how to [[#Second, choose which effect size to calculate?  choose which effect size to calculate]]  *how to [[#Second, choose which effect size to calculate?  choose which effect size to calculate]]  
*how to [[#Third, choose your statistical software  choose your statistical software]]  *how to [[#Third, choose your statistical software  choose your statistical software]]  
Line 54:  Line 54:  
==What is a metaanalysis?==  ==What is a metaanalysis?==  
===Definition===  ===Definition===  
+  A metaanalysis is...  
+  
+  combines the results of several studies that address a set of related research hypotheses.  
+  
+  Just as an individual study collects data from many individuals (data points) that is statistically summarized to answer the question of interest, a metaanlay  
+  
+  The results of each individual study are converted to a standardized effect size. A metaanalysis combines...  
+  
+  
+  
===Three Basic Questions===  ===Three Basic Questions===  
:A metaanalysis answers three general questions:  :A metaanalysis answers three general questions:  
Line 70:  Line 80:  
==How do I conduct a metaanalysis?==  ==How do I conduct a metaanalysis?==  
  ===First, choose  +  ===First, choose which statistical approach suits your needs=== 
:There are generally three different statistical approaches to conduct a metaanalysis 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 MetaAnalytic Approaches. Journal of Applied Psychology, 80, 94106). Some basic information from that article is posted below to get you started:  :There are generally three different statistical approaches to conduct a metaanalysis 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 MetaAnalytic Approaches. Journal of Applied Psychology, 80, 94106). Some basic information from that article is posted below to get you started:  
#'''Hedges & Olkin Approach''' – see [[Hedges, 1981]]; [[Hedges, 1982]]; [[Hedges & Olkin, 1985]]  #'''Hedges & Olkin Approach''' – see [[Hedges, 1981]]; [[Hedges, 1982]]; [[Hedges & Olkin, 1985]]  
Line 78:  Line 88:  
===Second, choose which effect size to calculate?===  ===Second, choose which effect size to calculate?===  
+  :asdfadsfsdf  
+  #  
+  #  
+  #  
===Third, choose your statistical software===  ===Third, choose your statistical software===  
+  :asdfasdfds  
+  #  
+  #  
+  #  
  +  ==If you want more detailed information about...==  
+  ===...the Hedges & Olkin approach...===  
  
+  ===...the Rosenthal & Rubin approach...===  
  ===  +  
+  ===...the Hunter, Schmidt, & Jackson approach...===  
  
Line 106:  Line 125:  
* What is the good number of studies to have bare minimum for a metaanalysis? A metaanalysis with 10 studies have been published before but is not recommended.  * What is the good number of studies to have bare minimum for a metaanalysis? A metaanalysis with 10 studies have been published before but is not recommended.  
  +  
* In a metaanalysis, have judge rate each variable across studies, one moderator at a time, instead of rating all variables in a single study before moving on to next study.  * In a metaanalysis, have judge rate each variable across studies, one moderator at a time, instead of rating all variables in a single study before moving on to next study.  
* With metaanalysis coding with a high number of studies to code, such as 75+, can have some coders rate the entire set, but can also have some coders (undergrads) code only a subset as long there is overlap, so that more than 1 judge is rating each study.  * With metaanalysis coding with a high number of studies to code, such as 75+, can have some coders rate the entire set, but can also have some coders (undergrads) code only a subset as long there is overlap, so that more than 1 judge is rating each study. 
Revision as of 03:43, 18 July 2006
► Have you ever wanted to learn about metaanalysis or conduct a metaanalysis but didn't know where to start? This webpage is devoted to providing you expert opinion on what you need to know to start your own metaanalysis.
► With the thousands of metaanalyses conducted in all areas of psychology over the past few decades, there has been an everincreasing number of articles, books, and software programs devoted to how to conduct metaanalyses. Below, experts on metaanalysis provide their suggesstions on which which of the many sources of information are the most useful and why  so that the user has an easytouse starting place for learning everything about metaanalyses.
Contents 
Where should I start?
If you want to learn what is a metaanalysis...

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

What is a metaanalysis?
Definition
A metaanalysis is...
combines the results of several studies that address a set of related research hypotheses.
Just as an individual study collects data from many individuals (data points) that is statistically summarized to answer the question of interest, a metaanlay
The results of each individual study are converted to a standardized effect size. A metaanalysis combines...
Three Basic Questions
 A metaanalysis answers three general questions:
 Central tendency – The central purpose of a metaanalysis 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?
 Variability – There is always going to be some degree of variation between the outcomes of the individual studies that compose the metaanalysis. 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.
 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 metaanalysis:
 Define your hypothesis
 Locate the Literature
 Identify and input data
 Cacluate Effect Sizes
 Analyze Variables
How do I conduct a metaanalysis?
First, choose which statistical approach suits your needs
 There are generally three different statistical approaches to conduct a metaanalysis 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 MetaAnalytic Approaches. Journal of Applied Psychology, 80, 94106). Some basic information from that article is posted below to get you started:
 Hedges & Olkin Approach – see (Hedges, 1981); (Hedges, 1982); (Hedges & Olkin, 1985)
 Rosenthal & Rubin Approach – see (Rosenthal, 1991); (Rosenthal & Rubin, 1978); (Rosenthal & Rubin, 1988)
 Hunter, Schmidt, & Jackson  see (Hunter, Schmidt, & Jackson, 1982); (Hunter & Schmidt, 1990)
Second, choose which effect size to calculate?
 asdfadsfsdf
Third, choose your statistical software
 asdfasdfds
If you want more detailed information about...
...the Hedges & Olkin approach...
...the Rosenthal & Rubin approach...
...the Hunter, Schmidt, & Jackson approach...
 What is the good number of studies to have bare minimum for a metaanalysis? A metaanalysis with 10 studies have been published before but is not recommended.
 In a metaanalysis, have judge rate each variable across studies, one moderator at a time, instead of rating all variables in a single study before moving on to next study.
 With metaanalysis coding with a high number of studies to code, such as 75+, can have some coders rate the entire set, but can also have some coders (undergrads) code only a subset as long there is overlap, so that more than 1 judge is rating each study.
► Back to Research Tools mainpage