  The existence of immune or cured individuals in a population and whether
there is sufficient followup in a sample of censored observations on their
lifetimes to be confident of their presence are questions of major importance
in medical survival analysis. So far only a few candidates have been put
forward as possible test statistics for the existence of sufficient followup in
a sample. Here we investigate one such statistic and give a detailed analysis,
obtaining an exact finite sample as well as asymptotic distributions for it,
and use these to calculate the power of the test as a function of the followup
in the sample.
