The CHUM: A frame supplementation procedure for address-based sampling
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.