How to Calculate Heterogeneity
Heterogeneity is a crucial concept in meta-analysis, reflecting the variation in effect sizes among studies. Calculating heterogeneity helps assess the reliability and generalizability of research findings. This guide walks you through the process with our interactive calculator.
- Enter the effect sizes of three studies in the respective fields.
- Click the “Calculate” button.
- View the results below the calculator, including the I² statistic and a visual representation using a bar chart.
The I² statistic, ranging from 0% to 100%, measures the proportion of total variation in study effects due to heterogeneity. It’s calculated as:
I² = (Q – df) / Q * 100%
where Q is the Cochrane’s Q statistic, and df is the degrees of freedom (number of studies minus 1).
| Study | Effect Size |
|---|---|
| 1 | 0.45 |
| 2 | 0.32 |
| 3 | 0.58 |
- Always interpret I² in conjunction with the p-value for Q to make a more informed decision about heterogeneity.
- Consider using a random-effects model for meta-analysis if I² is high (e.g., >75%).
What does a high I² value indicate?
A high I² value (e.g., >75%) suggests that there is a significant amount of variation or inconsistency among the included studies’ results.
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