This PDF document was made available from www.rti.org as a public service of RTI International. More information about RTI Press can be found at http://www.rti.org/rtipress. RTI International is an independent, nonprofit research organization dedicated to improving the human condition by turning knowledge into practice. The RTI Press mission is to disseminate information about RTI research, analytic tools, and technical expertise to a national and international audience. RTI Press publications are peerreviewed by at least two independent substantive experts and one or more Press editors. Abstract ii Introduction 1 Types of Supplementation Procedures 2 The CHUM Methodology 3 CHUM Operational Issues 6 Benefits and Limitations of Using ABS with CHUM 8 Summary 10 References 10 About the Authors Bonnie E. Shook-Sa, MAS, is a research statistician at RTI International. Her research focuses on sampling frame development and evaluation, sample design and optimization, and the analysis of complex data for household and establishment surveys. Rachel M. Harter, PhD, is a senior research statistician and program director at RTI. Areas of interest include household and establishment surveys, area probability survey designs, address-based sampling, imputation, and small area estimation. Joseph McMichael, BS, is a research statistician in RTI's Division for Statistical and Data Sciences. Jamie Ridenhour, MStat, is a research statistician at RTI. Her research interests are sample design, weighting, and methodological challenges associated with addressbased sampling and dual-frame random-digit-dial surveys. Jill A. Dever, PhD, is a senior research statistician at RTI. Her current research interests are variance estimation with calibrated analysis weights for complex survey designs and statistical issues related to samples drawn without a defined probabilistic structure.Abstract RTI developed the check for housing units missed (CHUM) methodology to compensate for housing unit undercoverage of address-based sampling (ABS) frames for in-person, area probability surveys. The CHUM systematically identifies housing units missing from the ABS frame, giving each housing unit a chance of selection with known probability. The CHUM poses several advantages over alternative supplementation approaches. Because only a subset of housing units within selected areas must be evaluated, the CHUM is less costly than supplementation techniques that require the verification of all addresses within selected areas. Because it is conducted after housing units are selected instead of the frame-building stage, the CHUM provides timelier frame updates. This paper presents details for designing ABS studies that incorporate the CHUM, appropriately incorporating missed units into area probability samples, and training field personnel to implement the CHUM. It also compares the CHUM with other frame supplementation approaches and discusses the advantages and limitations of each approach.