BMC Medical Research Methodology

Table 2 Kaplan-Meier and cumulative incidence estimators of probability of clinical stability for artificial data

From: How to handle mortality when investigating length of hospital stay and time to clinical stability

				Kaplan-Meier			Cumulative Incidence
t _i	y _i	s _i	d _i	${\hat{S}}_{c s} (t_{i})$	$1 - {\hat{S}}_{c s} (t_{i})$	SE	$\hat{S} (t_{i})$	${\hat{C I}}_{c s} (t_{i})$	SE
2	10	2	0	1-2/10 = 0.80	0.20	0.126	1-2/10 = 0.8	2/10 = 0.2	0.133
3	8	0	1	0.80	0.20	0.126	0.8*(1-1/8) = 0.7	0.2+0/8*(0.8) = 0.2	0.133
4	7	1	0	0.8*(1-1/7) = 0.69	0.31	0.151	0.7*(1-1/7) = 0.6	0.2+1/7*(0.7) = 0.3	0.154
5	6	1	1	0.69*(1-1/6) = 0.57	0.43	0.164	0.6*(1-2/6) = 0.4	0.3+1/6*(0.6) = 0.4	0.167
7	4	1	0	0.57*(1-1/4) = 0.43	0.57	0.174	0.4*(1-1/4) = 0.3	0.4+0/4*(0.4) = 0.5	0.172
>7	3			0.43	0.57		0.3	0.5

t _i = ith time point; y _i = number at risk at time t _i; s _i = number clinically stable at time t _i; d _i = number who died at time t _i; $Ŝ (t_{i}) = event free survival at time t_{i}$ = event free survival at time t _i; SE = standard error

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ISSN: 1471-2288

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