Nonresponse Bias in a Dual Frame Sample of Cell and Landline Numbers

We conducted a dual frame survey of landline and cell phone numbers in 2004 to evaluate the feasibility of including cell phone numbers in random digit dial telephone surveys in the United States. By sampling cell phone numbers, the coverage bias associated with households that have only cell phones is eliminated. However, we discovered two major sources of nonresponse bias in the dual frame sample. In an attempt to reduce these biases, we applied several different estimation schemes. But a comparison to the 2004 Current Population Survey Cell Phone Supplement showed that none of the estimation schemes substantially reduced the nonresponse bias of the estimates. We suggest other methods that might be used in future surveys that include cell phones and discuss the need for additional data collection and research on this issue.