  In interval censored models with current status observations, the variables
are indicators of the presence of individuals on observation intervals and
covariates. When several individuals share the same observation interval, a
simple procedure provides new estimators for the distribution of the
observation times and their intensity, in a closed form. They are
$n^{1/2}$-consistent for piece-wise constant covariates. Estimators of the
sample-sizes are deduced and asymptotic $\chi^2$ tests for independence of the
observations on consecutive intervals and for independence between consecutive
classes for the observed individuals are proposed.
