Coverage Gap: Out-of-State Phone Numbers for State Surveys
Marcus Berzofsky
RTI International
Caroline Scruggs
RTI International
Howard Speizer
RTI International
Bo Lu
Division of Biostatistics, The Ohio State University
Timothy Sahr
Ohio Colleges of Medicine Government Resource Center
As survey designers contemplate using a single frame cellphone design for telephone RDD surveys they consider the potential for coverage bias. From a coverage perspective, there has been discussion about the impact of excluding landline only households. There has not been as much consideration to the impact on coverage bias regarding residents of an area of interest who do not have a telephone number associated with that area. Unlike with landline numbers, a cellphone number is portable and therefore many residents of an area to be studied might not have a phone number associated with the area. In this presentation, using data from the 2017 Ohio Medicaid Assessment Survey, we try to measure the undercoverage rates due to cellphone-only population that don't appear to live within the survey area. We also examine two approaches to reduce coverage bias for persons with out-of-state telephone numbers that live within the area of interest. Our research found those with out-of-state cellphone numbers are different from those with an in-state phone number and there is likely coverage bias in a traditional RDD frame which excludes person with an out-of-state phone number.