Meta-analysis

(Difference between revisions)
 Revision as of 01:05, 18 July 2006 (view source)Stenstro (Talk | contribs)← Older edit Revision as of 01:15, 18 July 2006 (view source)Stenstro (Talk | contribs) Newer edit → Line 6: Line 6: ==Where should I start?== ==Where should I start?== *If you want to learn what is a meta-analysis... *If you want to learn what is a meta-analysis... - #For the '''basics''' behind meta-analyses see below where we lay out: + :For the '''basics''' behind meta-analyses see below where we lay out: ::the [[#Definition | definition]] of a meta-anlaysis, ::the [[#Definition | definition]] of a meta-anlaysis, ::the [[#Three Basic Questions | three basic questions]] answered by a meta-analysis, ::the [[#Three Basic Questions | three basic questions]] answered by a meta-analysis, ::the [[#Five Basic Steps | the five steps]] involved in a meta-analysis, ::the [[#Five Basic Steps | the five steps]] involved in a meta-analysis, - #For more '''in-depth''' discussion and explanations, we recommend... + :For more '''in-depth''' discussion and explanations, we recommend... ::start first with ::start first with :: :: :: :: *If you want to start conducting a meta-analysis... *If you want to start conducting a meta-analysis... - #For the '''basics''' behind conducting a meta-analysis see below were we lay out: + :For the '''basics''' behind conducting a meta-analysis see below were we lay out: ::how to [[#First, choose what statistical approach suits your needs | choose a statistical approach]] to conducting a meta-analysis, ::how to [[#First, choose what statistical approach suits your needs | choose a statistical approach]] to conducting a meta-analysis, ::the [[ ::the [[ ::the [[ ::the [[ - #For more '''in-depth''' + :For more '''in-depth''' discussion and explanations, we recommend... - ::start first with '''[[Johnson, Mullen, & Salas, 1995]]''' (Comparison of Three Major Meta-Analytic Approaches. Journal of Applied Psychology, 80, 94-106). + ::start first with '''[[Johnson, Mullen, & Salas, 1995]]''' which provides a statistical comparision of the three major meta-analytic approaches. :: :: :: ::

Revision as of 01:15, 18 July 2006

Meta-analysis

have you ever wanted to learn about meta-analysis or conduct a meta-analysis but didnt know where to start? This webpage is devoted to providing

Where should I start?

• If you want to learn what is a meta-analysis...
For the basics behind meta-analyses see below where we lay out:
the definition of a meta-anlaysis,
the three basic questions answered by a meta-analysis,
the the five steps involved in a meta-analysis,
For more in-depth discussion and explanations, we recommend...
start first with
• If you want to start conducting a meta-analysis...
For the basics behind conducting a meta-analysis see below were we lay out:
how to choose a statistical approach to conducting a meta-analysis,
the [[
the [[
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.

What is a meta-analysis?

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

There are generally five separate steps in conducting a meta-analysis:
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)

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

• What is the good number of studies to have bare minimum for a meta-analysis? A meta-analysis with 10 studies have been published before but is not recommended.
• In a meta-analysis, don’t have raters code conditions for which no effect sizes can be calculated.
• In a meta-analysis, 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 meta-analysis 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.

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