Measuring Heterogeneity (I² Statistic)

Learning Objectives

By the end of this section, you will be able to:

  • Understand the concept of heterogeneity in meta-analysis
  • Calculate and interpret the I² statistic
  • Use heterogeneity assessments to inform analysis decisions

Introduction

Heterogeneity refers to the variability or differences between study results in a meta-analysis. Measuring heterogeneity helps determine the appropriateness of pooling data.

Understanding the I² Statistic

  • Quantifies the percentage of total variation across studies due to heterogeneity.
  • Values range from 0% to 100%, with higher values indicating more heterogeneity.
  • Helps decide whether to use fixed-effects or random-effects models.

Interpreting I² Values

  • 0-25%: Low heterogeneity
  • 25-50%: Moderate heterogeneity
  • 50-75%: Substantial heterogeneity
  • 75-100%: Considerable heterogeneity

Conclusion

Measuring heterogeneity using the I² statistic is essential for understanding study variability and guiding analysis choices in meta-analysis.

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