We know that "unintentional” smart phone survey takers are different demographically and behaviorally and that their survey-taking experience is quite different from respondents who take surveys on PCs or other larger format devices. But we can’t know the extent to which those observed differences are the result of who chooses to start a survey on a mobile device and to what extent they are driven by the device on which they choose to participate. This presentation addresses several key questions including: How does question presentation or the usability of a survey instrument impact results? Can we meaningfully combine data from mobile and non-mobile responders when they’ve each taken a survey optimized for their respective devices? Will a mobile-friendly design decrease drop-offs and survey lengths for smart phone responders?