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! (It is defined as an increase of one standard deviation)
Below is Hattie’s table of effect sizes.