ABSTRACT
Samples obtained when selection and/or observation is restricted over some portion of the sample space are, depending on the nature of the restriction, designated as either truncated or censored. Truncated samples are those from which certain population values are entirely excluded. It is perhaps more accurate to state that truncation occurs to populations, and samples described as being truncated are in fact samples from truncated populations. Censored samples are those in which sample specimens with measurements that lie in the restricted areas of the sample space may be identified and thus counted, but are not otherwise measured. In some of the earlier references, censored samples were described as truncated with a known number of missing (unmeasured) observations. According to Hald (1949), J. E. Kerrich first suggested use of the designation "censored" for these samples. In practical applications, truncated samples arise from various experimental situations in which sample selection is possible over only a partial range of the variable. Examples of this type occur frequently in manufacturing when samples are selected from production that has previously been screened to remove items above and/or below specification values. Censored samples often result from life testing and reaction time experiments where it is common practice to terminate observation prior to failure or reaction of all sample specimens.
