Progressively censored variables sampling plans for two-parameter exponential distributions

Progressive censoring is quite useful in many practical situations where budget constraints are in place or there is a demand for rapid testing. Balasooriya & Saw (1998) present reliability sampling plans for the two-parameter exponential distribution, based on progressively censored samples. However, the operating characteristic (OC) curve derived in their paper does not depend on the sample size. This seems to be because, in their computations, they forget to consider the proportion of uncensored data, which also has an important influence on the subsequent developments. In consequence, their OC curve is only valid when there is no censoring. In this paper, some modifications are proposed. These are needed to obtain a proper design of the above sampling plan. Whenever at least two uncensored observations are available, the OC curve is derived in closed form and a procedure for determining progressively censored reliability sampling plans is also presented. Finally, the example considered by Balasooriya & Saw is used to illustrate the results developed in this paper for several censoring levels.