Categorical Data Analysis Using The SAS® System, 2nd Edition

17.2. Life Table Estimation of Survival Rates

Consider Table 17.1. Investigators were interested in comparing an active and control treatment to prevent the recurrence of a medical condition that had been healed. They applied a diagnostic procedure at the end of the first, second, and third years to determine whether there was a recurrence (based on Johnson and Koch 1978).

Table 17.1. Recurrences of Medical Condition

	Withdrawals			Recurrences
Treatment	Year 1	Year 2	Year 3	Year 1	Year 2	Year 3	No Recurrence	Total
Control	9	7	6	15	13	7	17	74
Active	9	3	4	12	7	10	45	90

The survival rate, or the waiting time rate, is a key measure in the analysis of time-to-event data. It is written

S(y) = 1 – F(y) = Pr{Y ≥ y}

where Y denotes the continuous lifetime of a subject and F(y) ...