A method to obtain the estimates for parameters and the size of
fragile population and their confidence intervals in the trunsored
and truncated models is introduced. When the censoring time becomes
large, the width of the confidence interval for the size of fragile
population in the trunsored model tends to a positive constant
value, whereas that in the truncated model tends to zero.
A typical example of the method applied to the case fatality ratio
of SARS shows different confidence intervals between the trunsored
model and the truncated model.