Effects of enhanced calling efforts on response rates, estimates of health behavior, and costs in a telephone health survey using random-digit dialing.

Public health researchers frequently rely on random-digit dialing (RDD) telephone surveys in monitoring trends in health behavior and evaluating health promotion interventions. RDD response rates have declined during the past decade, and cost-effective methods to increase response rates are needed. The authors evaluated two levels of enhanced calling efforts in an RDD survey of cancer-related health behavior in the State of Washington. The first level of enhanced calling effort was 1 month after 11 original calling attempts to a household, when the authors attempted up to 11 recalls. The second level was 6 months after the first answered call, when the authors recalled those persons who could not be interviewed. Enhanced calling efforts increased the overall survey response rate by 11 percent. Nine percentage points of the increase were attributable to call backs. There were demographic differences among the participants reached at different levels of calling effort, but no consistent associations of level of calling effort with health behavior related to alcohol use, smoking, diet, or health screening. Marginal costs for interviews completed with enhanced calling efforts were about 50 percent higher than costs for interviews reached in the first 11 calls. The authors concluded that enhanced calling efforts may be justified, because they increase confidence in the generalizability of survey results. However, the authors found very little change in survey results by including interviews from persons who were difficult to reach and to interview.