John Hattie’s effect sizes are a widely used measure of the impact of educational interventions. Hattie is an educational researcher who has been studying the effectiveness of various educational practices for over 20 years. His work has been influential in shaping educational policy around the world. In this article, we will explore what effect sizes are, how they are calculated, and why they are important in educational research.
Effect sizes are a statistical measure of the magnitude of an effect or intervention. They are used to compare the effectiveness of different educational interventions. The effect size tells us how much of an improvement in learning we can expect to see from a particular intervention. The larger the effect size, the more effective the intervention is likely to be.
Hattie’s approach to calculating effect sizes is based on a meta-analysis of hundreds of studies. A meta-analysis is a statistical technique that combines the results of many individual studies to create a larger sample size. Hattie’s meta-analysis included over 800 meta-analyses of educational interventions, covering over 50,000 individual studies.
Hattie’s approach to effect sizes is unique in that he uses a common metric, called the “d” value, to compare the effectiveness of different interventions. The “d” value represents the difference between the intervention group and the control group, divided by the standard deviation of the control group. The larger the “d” value, the more effective the intervention.
Hattie’s work has identified several interventions that have large effect sizes. For example, he found that feedback has an effect size of 0.73, which is considered a large effect size. This means that providing students with feedback about their learning can improve their performance by almost one standard deviation. Another intervention with a large effect size is meta-cognition, which has an effect size of 0.69. Meta-cognition is the ability to think about one’s own thinking and learning. Teaching students to become more aware of their own thinking processes can improve their learning outcomes significantly.
It is important to note that effect sizes are not the only measure of educational effectiveness. Other factors, such as the cost and feasibility of an intervention, must also be considered. However, effect sizes are a useful tool for comparing the effectiveness of different interventions and for identifying interventions that are likely to have a significant impact on student learning.
In conclusion, John Hattie’s effect sizes are a valuable tool for educational researchers and practitioners. By using a common metric to compare the effectiveness of different interventions, Hattie has provided valuable insights into what works in education. His work has identified several interventions that have large effect sizes, such as feedback and meta-cognition, which can significantly improve student learning outcomes. Educational policy makers and practitioners can use this information to make evidence-based decisions about which interventions to implement in their classrooms and schools.
Reference: Hattie, J. (2009). Visible learning: A synthesis of over 800 meta-analyses relating to achievement. Routledge.