Fourth National Incidence Study of Child Abuse and Neglect (NIS–4)

design. The measure of size was the population of children under 18 years old in Census 2000.Large counties with a child population over 400,000 were selected with certainty. Undersizedcounties (those with fewer than 4,000 children) were combined with contiguous counties to formgeographically compact PSUs with sufficiently large populations to justify data collectionefforts. Constructing multi-county PSUs considered local CPS agency jurisdictions (whichusually, but not always, follow county boundaries) and limited the number of counties in a PSUto no more than six.Under this scheme, the 14 largest counties were selected with certainty, leaving alisting of 2,282 noncertainty PSUs nationwide, 1,685 of which were single-county and restmultiple-county PSUs. Statisticians allocated these noncertainty PSUs to 48 strata, based onCensus region, metro status, the NCANDS child victim substantiation rate, FBI crime rate, andpercentage of households headed by single females with children. (Choice of these factorsderived from prior analyses on predictors of child maltreatment rates.) Two PSUs were selectedfrom each stratum, using probability-proportionate-to-size (PPS) of the Census 2000 populationof children, which identified 96 noncertainty PSUs: 88 single-county PSUs, 6 two-county PSUs,1 three-county PSU and 1 five-county PSU. Thus, the final NIS–4 sample consisted of 110PSUs (14 certainty and 96 noncertainty), which included 122 counties—14 certainty and 108noncertainty counties.CPS agencies and cases. The CPS agency sample comprised all 126 CPS agenciesserving all or part of a sampled county. Most were county-level agencies serving individualcounties. Eligible CPS cases were those reported to these CPS agencies during the 13-weekstudy reference period and assigned for investigation. CPS case sampling followed the approachused in the NIS–3. Fatality cases were included with certainty. An approximately equalprobabilitysample was randomly selected from the remaining eligible cases. Sampled caseswere assigned to receive CPS Maltreatment data forms, while CPS Summary data forms wereassigned to the remaining eligible cases for use during unduplication and weighting, as describedin those sections. (The Data Collection section describes the different data forms.) Theseprocedures resulted in listings of 140,206 CPS case investigations during the study referenceperiods, and identified a sample of 11,930 of these for CPS Maltreatment data forms. To supportspecial analyses examining whether any of the children not investigated during the study periodwere reported to CPS and investigated later, the NIS–4 also obtained Summary data forms on allcases reported and assigned for investigation during the month following the reference period.The NIS–4 gathered an additional 38,398 Summary data forms for this component.A-4