Teachers toolbox - Professor John Hattie's Table of Effect Sizes
Hattie says ‘effect sizes' are the best way of answering the question ‘what has the greatest influence on student learning?'. An effect-size of 1.0 is typically associated with: • advancing learners' achievement by one year, or improving the rate of learning by 50% • a correlation between some variable (e.g., amount of homework) and achievement of approximately .50 • A two grade leap in GCSE, e.g. from a C to an A grade An effect size of 1.0 is clearly enormous! Below is Hattie's table of effect sizes. Terms used in the table (Interpreted by Geoff Petty) • An effect size of 0.5 is equivalent to a one grade leap at GCSE • An effect size of 1.0 is equivalent to a two grade leap at GCSE • ‘Number of effects is the number of effect sizes from well designed studies that have been averaged to produce the average effect size. • An effect size above 0.4 is above average for educational research Some effect sizes are ‘Russian Dolls' containing more than one strategy e.g. Beware Over-interpretation!