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 evalua ting health promotion interventions. RDD response rates have declined during the past decade, and cost-effective methods to increase respons e rates are needed. The authors evaluated two levels of enhanced calli ng efforts in an RDD survey of cancer-related health behavior in the S tate of Washington. The first level of enhanced calling effort was 1 m onth after 11 original calling attempts to a household, when the autho rs attempted up to 11 recalls. The second level was 6 months after the first answered call, when the authors recalled those persons who coul d not be interviewed. Enhanced calling efforts increased the overall s urvey response rate by 11 percent. Nine percentage points of the incre ase were attributable to call backs. There were demographic difference s among the participants reached at different levels of calling effort , but no consistent associations of level of calling effort with healt h 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 m ay be justified, because they increase confidence in the generalizabil ity of survey results. However, the authors found very little change i n survey results by including interviews from persons who were difficu lt to reach and to interview.