Mixed trunsored model with application to the lifetime estimation of malcondition items

Assuming that a system consisting of fragile and durable items will be broken if one of the items fails. In addition, we assume that the system also consisting of malcondition items or good condition items will not be broken even if all of the items are in malcondition. There is a suspect that an item in malcondition might someday be included in fragile items, but not strictly so. The time of failure is known, but the time when an item is changed from in good condition to in malcondition is unknown. Under such conditions, we want to estimate the probability distribution for the malcondition items. The mixed trunsored model can give the lifetime distribution for the items in malcondition