How To Calculate I Squared For Meta Analysis In Sas

Calculating i squared (I²) is a crucial step in conducting meta-analyses using SAS. I² measures the percentage of variability in effect estimates that is due to heterogeneity rather than sampling error.

1. Enter the value of ‘i’ in the provided input field.
2. Enter the value of ‘n’ in the next input field.
3. Click the ‘Calculate’ button to get the result.

The formula for calculating I² is:

I² = (Q – df) / (df)

where Q is the Cochran’s Q statistic and df is the degrees of freedom.

Comparison of I² values for different meta-analyses

• Always interpret I² values in the context of the number of studies included in the meta-analysis.
• Consider using other measures of heterogeneity, such as the Higgins I² statistic, for a more comprehensive understanding.

What is the difference between I² and Cochran’s Q statistic?

I² is a measure of the proportion of total variation in study effects that is due to heterogeneity, while Cochran’s Q statistic is a test of heterogeneity that follows a chi-square distribution.

For more information, refer to the following authoritative sources:

• CDC – Meta-Analysis
• PMC – The Cochrane Handbook for Systematic Reviews of Interventions