# Meta-analysis

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

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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 | 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 |

## Revision as of 00:09, 18 July 2006

Meta-analysis

Where should I start?
If you want to learn what is a meta-analysis…
If you want to start conducting a meta-analysis…

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

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

(table) email and ask them, tell them copyright law allows, plus…

If you want to follow the…

If you want to follow the…

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?

- 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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