Do In-person Interviews Reduce Bias in a Mixed- Mode Survey of Persons with Disabilities?*

For people with certain disabilities, completing an interview by telephone or mail may be difficult or impossible, making in-person interviews necessary. However, in-person interviews are generally more expensive than telephone or mail and may be cost prohibitive for large samples. The National Beneficiary Survey (NBS), sponsored by the Social Security Administration (SSA), is a multiwave survey of persons who receive Supplemental Security Income (SSI) or Social Security Disability Income (SSDI). The survey was conducted four times between 2004 and 2010 by Mathematica Policy Research using computer-assisted telephone interviewing (CATI) with computer-assisted personal interviewing (CAPI) follow-up for telephone nonrespondents.1 We achieved significant cost savings by limiting field operations to only those beneficiaries who could not be reached or interviewed by telephone. The mixed mode design also furnished higher response rates than would be achievable with a telephone-only design. The purpose of this analysis was to assess whether survey estimates woul