Introduction to random digit dial cell phone surveys

A growing concern for random digit dialing (RDD) surveys, such as the Behavioral Risk Factor Surveillance System (BRFSS), which generate a random sample of household landline telephone numbers, is the exclusion of adults living in cell phone only households. Recent data suggest that the validity of some health estimates based on traditional RDD surveys are increasingly questionable due to wireless substitution. The percent of adults who lived in cell phone or wireless only households has increased almost six-fold between early 2003 (2.9%) and mid 2008 (17.5%). Another 13.3% predominately use their cell phones for calls, despite having a landline telephone. Existing indicators suggest wireless substitution will continue to grow. Moreover, data suggests that this population differs from their landline-owning counterparts in important health and lifestyle characteristics. The potential for biased health estimates due to sample under-coverage remains a real and growing threat to RDD health surveys. Starting in 2009, the Center for Disease Control and Prevention (CDC) is requiring states to incorporate cell phone interviews in their regular BRFSS sample. Despite the increased recognition of the issue and the advances made in improving data collection procedures no widely accepted methods of evaluating data quality or data weighting exist to date, particularly for state and local area surveys. This proposed special session will provide an analysis of data quality of cell phone surveys, an assessment of bias in landline only surveys, and demonstrate weighting procedures for merging cell phone samples with landline samples.