The sample for the 2002 survey was selected from the universe of all jails in the United States, which were enumerated in the 1999 Census of Jails. The sample design was a stratified two-stage selection in which jails were selected in the first stage and inmates to be interviewed were selected in the second stage. In the first sampling stage, six separate strata were formed based on the size of the male, female, and juvenile populations in each jail. In strata one and two, all jails were selected to ensure jails with large numbers of males, females, or juveniles had a higher probability of selection than jails with a small inmate population. The weighting procedure consisted of a base weight for each inmate and four adjustment factors that produced the final weight for the survey. Data were collected through face-to-face interviews with jail inmates using computer-assisted personal interviewing.
Periodically, changes are made to the questionnaires to improve measurement and to collect new information on evolving issues in criminal justice and topics of greatest interest to the field and data users. Recent modifications include enhanced questions on medical and mental health histories of inmates. In 2002, the sample design was modified to ensure a representative sample of juveniles being held in local jails.