Types of Lifetime Data

This section describes various types of data that you can analyze with the RELIABILITY procedure.

Lifetime data for which the values of all sample units are observed are called complete data. This means that the failure times are observed for all units.

Many practical problems in life data analysis involve data for which some units are unfailed. The failure time for an unfailed unit is known only to be greater than the last running time. This type of data is said to be right censored, and the censoring time is used in the analysis of the data. Data for which censoring times are intermixed with failure times are sometimes called multiply censored or progressively censored.

Failure times may be known only to be less than some value. This type of data is called left censored.

Another common situation is where the failure times of units are not known exactly, but time intervals that contain the failure times are known. This type of data is called interval censored.

Interval-censored data for which all units share common interval endpoints are called readout, inspection, or grouped data.

Arbitrarily censored data can contain a combination of failures, right-, left-, and interval-censored data.