random sample

n. a set of records within a records series that are chosen for permanent retention through a statistical process that ensures each file within the series has an equal chance of being included in the retained set a set of records within a records series that are chosen for permanent retention through a process that employs a preset pattern of selection to produce a sample of the whole a set of records within a records series 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 it was within the whole

Notes

The random sample may be divided into three subcategories: simple random, stratified random, and systematic random. The first, the simple random sample, is a pure form of the process: the records in the sample are chosen via a totally random process based on the necessary sample size for the body of records. If the records in play are quite homogenous and there is no need to save them in their entirety, the simple random sample is likely the best methodology. A systematic random sample (also known as a systematic sample) is one without absolute randomness; instead, a pattern of selection is employed. Systematic samples include those that consist of every 100th file in a series, all records from years ending with a 0 or a 5, or every tenth file within each set of 100 files that occurs after each randomly selected filed in a series. A stratified random sample (also known as a stratified sample) is a type of sample created only when working with a heterogeneous set of records. In a set of case files with different types of cases that take up different percentages of the files, a stratified sample can ensure that a statistically valid sample is created for each case type. For instance, a stratified sample of a series of criminal court case files would consist of a simple or systemic random sample that was statistically valid for each type of crime (or each stratum) of the series.