The present study proposes several methods for improving the parameter estimation of interval-censored exponential lifetime data. These methods can be regarded as the versions of substitution method which are based on the most probable time of occurring failures or the meantime of failures in each inspection interval. Based on simulation studies, the methods proposed in this present study can improve the existing estimators which are based on the midpoint of inspection intervals “, or”,the exponential probability plot.

In this research, new estimators for the hazard rate of exponential distribution in interval censored data are compared with some existing methods based on simulation studies. Then the asymptotic distribution of one of the introduced methods that has better performance is obtained.