Geographic Accuracy of Cell Phone RDD Sample Selected by Area Code Versus Wire Center

at National Center for Health Statistics, CDC

The assignment of geographic location to cell phone numbers in RDD cell phone sample frames is often inaccurate. This inaccuracy can potentially lead to increased cost and bias for area-specific telephone surveys and increase variance for national telephone surveys with area stratification (Skalland and Khare, 2013). The assignment of a cell phone number to a geographic location in the construction of the sample frame can be based on the area code of the phone number, location of the wire-center associated with the phone number, or rate center associated with the phone number. In this paper, we compare state and local-area geographic accuracy rates of cell phone numbers assigned to a geographic location based on the area code of the phone number versus the wire center associated with the phone number using data from the National Immunization Survey (NIS), a dual-frame RDD survey sponsored by the Centers for Disease Control and Prevention and fielded by NORC at the University of Chicago. Reported geography from NIS survey respondents is compared to geographic information from the cell phone sample frame and accuracy rates associated with geographic classification assessed. In addition, we present differences in demographic distributions between survey respondents with accurate geographic classification and respondents with inaccurate geographic classification for both the area code and the wire center approaches.