Table 2. Comparison of fitness of different parametric frailty models based on the Akaike information criteria, June 2018.

Baseline distribution	Frailty distribution	Log- likelihood	K	c	AIC Value
Exponential	Gamma	-1404	10	1	2829
Weibull	Gamma	-603	10	2	1229
Log-logistic	Gamma	-1343	10	2	2711
Log-normal	Gamma	-1334	10	2	2691

AIC = -2lnL + 2(k +c), where c is the number of model-specific distributional parameters & k is the number of model covariates.