Use of a Targeted Sequential Mixed Mode Protocol in a Nationally Representative Panel Study.

Relatively low response rates in mixed mode studies remain a concern. Whether targeting protocols to match respondents' likely mode is an effective strategy remains unclear. For those without a clear likely mode, how the details about sequencing influence response rates, mode, field work effort, and potential response bias remain important questions. This article describes a targeted sequential design implemented in a 2016 mixed mode supplement with individuals ages 30 and older in the Panel Study of Income Dynamics, the longest running national panel study in the US (N=10,784). Respondents predicted to be likely to respond by web were invited to a web study and sent a paper copy after 6 weeks (web-first); those likely to respond by paper were also invited to participate by web but told that a paper copy would be sent shortly (signal-and-send). An embedded experiment measured the impact of the two protocols among a group of respondents with no clear likely mode (N=889). Over 40% of individuals with no likely mode are under the age of 40, and the group falls between the likely web and paper groups in terms of education and internet use and includes more women and single respondents. Compared to the likely web and paper groups, those with no likely mode had lower response rates and required more fieldwork effort. Among those randomly assigned, the signal-and-send protocol increased response over the web-first protocol from weeks 4 through 7. By week 16, both protocols yielded similar response rates (AAPOR 1 RR=71% vs. 68%, p=0.49), field effort (7.9 vs. 8.4 mean weeks, p=0.251), and distributions of respondent characteristics. Among those responding, cases randomized to web-first were more likely than those randomized to signal-and-send to respond by web (62.7% vs. 42.4% p<.001). We discuss implications for targeted protocols in mixed mode panel surveys.