n.a portion, within a body of records, selected for permanent retention because it meets criteria for selection set by the appraisal archivistHam 1993, 78In a purposive sample, the goals of selection are determined by the selector’s judgment, not by some mathematical formula. Variously called purposive, judgmental, selective, or subjective sampling, it is the method most familiar to and used by archivists.Lyle 2004, 7The Dutch Ministry of Justice, for example, used a purposive sample of its one million personal files to select “files which are formed in deviation from the rules. Here, only the exceptions (around 3 percent of the total) to the common practice are preserved”. Unfortunately, purposive sampling is also highly prone to human bias and selection error. Through dealing subjectively with the appraisal process, one’s samples are skewed toward personal feelings and cannot be taken as representative of the whole.Yakel et al. 2008, 331We wanted to conduct approximately forty interviews so we created a purposive sample from these volunteers taking into account IR stage of development (from no planning or only planning to implementation and planning and pilot testing), geographic region, the size and Carnegie classification of parent institution (from small colleges to research universities), the range and types of content represented in the IR, and the position of respondents.Dryden 2014, 67The study population was a purposive sample of 96 repositories drawn from nearly 500 institutional members of the Society of American Archivists (SAA).
A purposive sample has no random element to it. Instead, the archivist sets criteria that are characteristics of important records and then compares each file to those criteria to decide which records are retained. The purposive sample is not statistically valid, so it is used with relatively heterogeneous records as a way of separating the archival wheat from the nonpermanent chaff.