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

UNDUPLICATION NIS provides estimates of the numbers of maltreated children, so it is critical for thestudy to avoid counting the same child more than once. The purpose of unduplication is toidentify children who enter the study data on multiple data forms and reduce their information toa single record for analysis. Unduplicating NIS–4 data consisted of three main steps:• Identifying child-level records that may be duplicates (candidate pairs)• Deciding whether the candidate pair records were true duplicates• Unifying duplicate recordsCandidate pairs. Matches on subsets of 8 key data items helped to identifycandidate pairs:First name AgeLast name initial Ethnicity/raceGenderCity of residenceDate of birth Number of children in householdCandidate pairs for child-level records from CPS Maltreatment and Sentinel dataforms were identified 3 ways:• Manually using a computerized sorting system• Using the NIS–3 rule-based algorithm that identified 2 of 3 matching patterns• Using a probability-based matching software designed to identify matchesDuring the first stage, all data forms in 9 small counties were examined manually.This entailed unduplication staff sorting all the child-level records in each county by various keydata items and flagging pairs of records that appeared to be potential duplicates. Statisticiansused the data in these counties and these initial candidate-duplicate decisions to guide thesettings of parameters on the probability-based matching software so that it would, as closely aspossible, identify the same candidate pairs. In addition, the unduplication task leader adjustedthe NIS–3 rule-based algorithm so that it would not generate numerous false-positive candidates.Once these preparations were completed, the adjusted NIS–3 rule-based algorithm and theA-23