35 – Frame and Coverage Issues
An Evaluation of Ported Telephone Numbers in the 2013 California Health Interview Survey
Greg Norman
Westat
Ismael Flores-Cervantes
Westat
In telephone surveys, ported numbers are those telephone numbers originally assigned as a wireline that are subsequently converted to wireless service. These ported numbers are sampled as a part of a landline sample and identified as wireless during the post-sampling processing. Ported telephone numbers, as of 2013, represent a small but growing proportion in landline samples, and there is little research on their characteristics. In some survey operations, ported numbers are excluded from data collection, while in others they are dialed as a part of a cell phone sample. In the California Health Interview Survey (CHIS), a representative dual-frame random digit dialed (RDD) telephone survey of the California non-institutionalized population, ported telephone numbers have been sampled and dialed as a part of the cell phone sample since 2007. In the 2013 CHIS, sampling and subsequent processing identified over 10,000 ported telephone numbers. This paper analyzes the results of dialing these ported telephone numbers and compares their respondents' characteristics to those from both the landline and cell phone samples to assess potential bias if the ported numbers are excluded in data collection.