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

2.5 UnduplicationThe NIS provides estimates of the number of children who are maltreatedduring the study year. However, the NIS can receive more than one data formconcerning an individual child. Such duplicates occurred when more than one studysource recognized the same maltreatment event and when a given child experienced morethan one maltreatment event during the study reference period. In either case, it wasnecessary to identify and resolve all such duplicate child records to ensure that theestimates would reflect the child as a unit of measurement. Following the approach takenin the previous studies, only enough close-to-identifying information was obtained in theNIS–4 to allow fairly certain judgments as to whether or not two data forms described thesame child. Decisions about duplicates relied on matches on the child’s sex, first name,last initial, date of birth or age, race, city of residence, and number of other children inthe household.Having identified duplicates, the NIS retained only one record to representthe individual child in the analysis database. Selecting a single record to represent anunduplicated child followed similar decision rules to those used in previous NIS cycles,giving preference to records with countable maltreatment under the definitionalstandards, to those with more complete demographic information, to records fromsources higher in the traditional NIS hierarchy of recognition sources (iceberg model inFigure 2–1), 13 and to those describing more forms of maltreatment. Statisticians assignedthe unified child record a weight that adjusted for the multiple probabilities of samplingthe child from the sources represented in the duplicate grouping.The NIS–4 unduplication team processed 30,543 child records. Afteridentifying and unifying duplicate records, the final database contained 29,488 records onindividual children.The NIS–4 Analysis Report (Sedlak, Mettenburg, Winglee et al., 2010)details the NIS–4 unduplication process.13 Chapter 7 provides further details about this recognition source priority system.2–15