Hattie Effect Size Calculator

Historical Background

The "Hattie Effect Size" is derived from John Hattie's influential meta-analyses on educational interventions. John Hattie, a renowned education researcher, analyzed thousands of studies to determine what factors most effectively influence student learning. Effect size, denoted as Cohen's d, is a standardized measure of the magnitude of an intervention's impact.

Hattie used effect sizes to rank different educational strategies and their influence on student achievement, identifying that an effect size above 0.4 is considered above average in the context of education. This insight has been instrumental in guiding educators to prioritize high-impact strategies.

Calculation Formula

The formula for calculating effect size (Cohen's d) is:

\[ d = \frac{M{\text{post}} - M{\text{pre}}}{SD} \]

Where:

• \( M_{\text{post}} \) = Mean post-test score
• \( M_{\text{pre}} \) = Mean pre-test score
• \( SD \) = Standard deviation of scores

Example Calculation

Suppose a study evaluates an educational program where:

• The mean pre-test score is 60.
• The mean post-test score is 75.
• The standard deviation of scores is 15.

Using the formula:

\[ d = \frac{75 - 60}{15} = \frac{15}{15} = 1.0 \]

This indicates a large effect size, meaning the intervention had a substantial impact.

Importance and Usage Scenarios

Effect size is crucial in determining the effectiveness of educational interventions. It helps educators and researchers compare the impact of different teaching strategies objectively. For example:

• An effect size of 0.2 is considered small, meaning a minor effect.
• An effect size of 0.5 is moderate.
• An effect size of 0.8 or above is considered large, indicating a strong effect.

Hattie's work showed that an effect size of 0.4 or more is needed to signify a meaningful impact on student learning, often referred to as the "hinge point."

Common FAQs

1. What is the Hattie Effect Size?

   • It is a measure used to quantify the impact of educational interventions on student outcomes, based on John Hattie's meta-analytic studies.

2. What is a good effect size according to Hattie?

   • According to Hattie, an effect size above 0.4 is considered to have a positive impact on student learning.

3. How is effect size useful for educators?

   • Effect size helps educators identify which interventions are most effective, allowing for data-driven decision-making to improve student achievement.

4. Can effect size be negative?

   • Yes, a negative effect size indicates that an intervention led to a decrease in outcomes compared to the baseline, implying a negative impact.

This calculator can be a helpful tool for researchers and educators who want to quickly determine the effect size of their interventions, facilitating evidence-based practices in education.