Hattie's Research - What is a "meta analysis"?

 It is a method that uses statistical techniques to combine results from different studies and obtain a quantitative estimate of the overall effect of a particular intervention or variable on a defined outcome—i.e., it is a statistical process for pooling data from many studies to glean a clear answer. Meta-analysis produces a stronger conclusion than can be provided by any individual study.

The process of meta-analysis is as follows:

1. Identify an outcome
2. Identify an influence
3. Research to find studies that include the outcome and the influence
4. Determine effect sizes
5. Establish comparisons

To illustrate this, the "homework" example can be used:
Outcome = student achievement
Influence = homework
Research = 59 studies from past 20 years
Effect = (d=0.40 overall, d=0.5 for secondary and d=-0.08 for primary)
Conclusion - Secondary students are better able to self-regulate and monitor their work and time.