Table 3.

Performance Characteristics of Individual and Multilevel Models.

	Full Population
Statistic	Individual Level	+ Multilevel Data
Number of observations	59,234(0.02% missing data, n = 15)	58,040(2% missing data, n = 1194)
C-statistic	0.72	0.72
Bootstrap-corrected C-statistic	0.72	0.72
R2 (95% CI)	0.11	0.11
Integrated calibration index (ICI)	0.01	0.01
R2 statistic, represents the model’s predictive ability, the agreement between an individual’s predicted and observed risk of the event; ICI statistic represents the model's weighted difference between observed and predicted probabilities