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Table 5 Three level multilevel model (patient within surgeon within centre)

From: Clustering in surgical trials - database of intracluster correlations

Outcome ICC Estimate 95% CI*
EQ-5D 12 m Level 2 (surgeon) 0.417 (0.000, 0.857)
  Level 3 (centre) 0.012 (0.000, 0.003)
  Levels 2 (surgeon) and 3 (centre) 0.029 (0.005, 0.053)
  1. CI: confidence interval; EQ-5D: EUROQOL 5D-3L; ICC: Intracluster correlation coefficient.
  2. multilevel model using xtmixed command in Stata with no adjustment for treatment or other factors.
  3. * 95% bootstrapped (bias corrected and accelerated) confidence interval