Telephone sampling bias in surveying disability

Results of the California Disability Survey indicate that telephone interviewing is well suited for undertaking disability studies that provide (1) estimates of subgroups of the disabled population, including those that are statistically rare: (2) information on current and anticipated areas of policy concern; and (3) information for geographic areas important in rehabilitation program planning. Although these objectives necessitated a large sample size and a complex instrument, the costs and timeliness of telephone interviewing enabled the survey objectives to be reached. This paper discusses the advantages of telephone interviewing, as well as biases inherent in its use. The magnitude of the bias from the omission of nontelephone households is assessed, and the results confirm that the omission of nontelephone households introduces only minor biases into estimates for the total working-age population. A method of weighting is developed and illustrated.