  Frequent monitoring of participant compliance is necessary when conducting
large-scale, longitudinal studies to ensure that the collected data is of
sufficiently high quality. While the need for achieving high compliance has
been underscored and there are discussions on incentives and factors affecting
compliance, little is shared about the actual processes and tools used for
monitoring compliance in such studies. Monitoring participant compliance with
respect to multi-modal data can be a tedious process, especially if there are
only a few personnel involved. In this case study, we describe the iterative
design of an interactive visualization system we developed for monitoring
compliance and refined based on changing requirements in an ongoing study. We
find that the visualization system, leveraging the digital medium, both
facilitates the exploratory tasks of monitoring participant compliance and
supports asynchronous collaboration among non-co-located researchers. Our
documented requirements for checking participant compliance as well as the
design of the visualization system can help inform the compliance-monitoring
process in future studies.
