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Table 1 Calculation of the within-cluster, within-period correlation (WPC) and within-cluster, between-period correlation (BPC) for intensive care unit (ICU) log-length of stay (LOS) in the Australian and New Zealand Intensive Care Society – Adult Patient Database (ANZICS-APD)

From: Understanding the cluster randomised crossover design: a graphical illustration of the components of variation and a sample size tutorial

\( {\widehat{\sigma}}_{ICU}^2=0.045 \)  
\( {\widehat{\sigma}}_{CP}^2=0.008 \)  
\( {\widehat{\sigma}}_I^2=1.360 \)  
\( \widehat{\rho}=\frac{{\widehat{\sigma}}_{ICU}^2+{\widehat{\sigma}}_{CP}^2}{{\widehat{\sigma}}_{ICU}^2+{\widehat{\sigma}}_{CP}^2+{\widehat{\sigma}}_I^2}\kern0.5em =\kern0.5em \frac{0.045+0.008}{0.045+0.008+1.360}\kern0.5em =\kern0.5em 0.038 \)  
\( \widehat{\eta}=\frac{{\widehat{\sigma}}_{ICU}^2}{{\widehat{\sigma}}_{ICU}^2+{\widehat{\sigma}}_{CP}^2+{\widehat{\sigma}}_I^2}\kern0.5em =\kern0.5em \frac{0.045}{0.045+0.008+1.360}\kern0.5em =\kern0.5em 0.032 \)