stratified sample

n. a portion of a body of records that are chosen for permanent retention through a process that ensures the retention of a statistical sample of each type or category of file within the series in the retained set at the same percentage as each existed within the whole; a stratified random sample


The stratified sample ensures the statistical relevance of the sample hews to each population of record types or categories within the entire set of records being sampled. Each type of case, for instance, in a set of case files may take up a different percentage of the entire series, so the stratified sample ensures each case type is represented at the same percentage in the retained sample as it did in the series as a whole.