Geographical Accuracy of Cell Phone Samples and the Effect on Telephone Survey Bias, Variance, and Cost
Meena Khare
National Center for Health Statistics
Benjamin Skalland
NORC
Prior to sampling, geographic information can be derived from landline telephone numbers with great accuracy, allowing for state-specific landline surveys and effective geographic stratification for national surveys producing state-level estimates. However, the assignment of geographic information to cell-phone numbers is problematic because the cell-phone number is associated with the place the service for that cell-phone number was originally acquired, which is not necessarily the place where the person currently resides: a person could have acquired the service in a different state than the state of residence or could have moved to a different state since activation. Christian et al. (2009) estimate that less than 3 percent of landline households reside in a state that differs from the state associated with the landline telephone number, but about 12 percent of cell-phone-only adults reside in a state that differs from the state associated with the cell-phone number. In this paper, we present state-level estimates of the geographic inaccuracy of cell-phone samples for adults in cell-phone-only households from the National 2009 H1N1 Flu Survey. We then discuss the implications of cell-phone sample geographic inaccuracy on the bias and variance of dual-frame estimates, as well as on the cost of dual-frame surveys.
