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

SAMPLES The NIS target population is the set of children under 18 years of age who aremaltreated during the study period, including all who are reported to child protective services(CPS) agencies and accepted for investigation by those agencies and any others who come to theattention of community professionals working in specific categories of agencies (such as police,teachers, social workers, nurses, and child care providers).The three-stage sample design involves: (1) a first-stage, nationwide sample ofprimary sampling units (PSUs) that are single counties or clusters of contiguous counties, (2) asecond-stage selection of all CPS agencies and samples of sentinel (non-CPS) agencies withinthe selected PSUs, and (3) case-level samples of abused and neglected children in CPS agenciesand samples of sentinels (professionals who have direct contact with children) in sentinelagencies. The sampled sentinels are asked to report on all abused and neglected children thatthey encounter in the course of their work during the study reference period.The NIS–4 used two reference periods, one of which conformed to that used in theNIS–2 and NIS–3: a 3-month period from the first week in September 2005 through the firstweek in December 2005. The second reference period occurred the following spring, from thefirst week in February 2006 through the first week in May 2006. The CPS case samples wereselected retrospectively from records on all cases reported during the study reference period thatthe agency accepted for investigation. Sentinel data collection was prospective, with sampledsentinels asked to be on the lookout for maltreated children during the study reference period andto submit detailed data forms describing any such children they encounter.Compared with earlier NIS cycles, the NIS–4 substantially increased sample sizesand broadened sentinel agency coverage. Relative to the NIS–3, the NIS–4 essentially tripled thesamples of counties (from 42 to 122), CPS agencies (from 42 to 126), and CPS cases (from 3,368to 11,930) and nearly doubled the samples of sentinel agencies (from 981 to 1,679) and sentinels(from 5,889 to 11,321).Counties. The NIS–4 Primary Sampling Units (PSUs) were constructed from thelist of 3,141 counties in the 2000 Census. This list was updated to reflect county definitions andboundaries at the time of NIS–4 sampling in 2004. The NIS–4 selected a sample of 110 PSUs(122 counties) using a probability-proportional-to-size (PPS) sampling method and a stratifiedA-3