Adjustment for Noncoverage of Nonlandline Telephone Households in an RDD Survey

• Activity Number: 264
• Type: Contributed
• Date/Time: Tuesday, August 5, 2008 : 10:30 AM to 12:20 PM
• Sponsor: Section on Survey Research Methods
• Author(s): Sadeq R. Chowdhury and Robert Montgomery*+ and Philip J. Smith
• Companies: National Opinion Research Center and National Opinion Research Center and Centers for Disease Control and Prevention
• Keywords: noncoverage adjustment ; poststratification ; RDD survey

Abstract

The National Immunization Survey (NIS)---a nationwide, list-assisted RDD survey conducted by the NORC for the Centers for Disease Control and Prevention---monitors vaccination rates of children between the ages of 19 and 35 months. As in any RDD survey, non-landline telephone (i.e., no-phone and cell-only) households are not sampled in the NIS. To compensate for this noncoverage, a special adjustment (Keeter, 1995) is applied, in which households with an interruption in landline service are used to represent nonlandline households. With the increasing proportion of cell-only households among the nonlandline households, this adjustment may no longer be very effective. Also, the adjustment introduces a considerable variation in sampling weights. The paper evaluates the impact of this adjustment on bias and variance to assess the effectiveness and to identify an optimal level of adjustment.