This work was supported by a Genetics Education Research Program grant from the American Society of Human Genetics. We thank Dr. Thomas Kim for suggesting the multiple-select format and Dr. Brian Couch for help with statistical issues for this kind of instrument. We are grateful to the Science and Mathematics Education Research Collaborative at the Rochester Institute of Technology, the Biology Education Research group, Dr. Ross Nehm, and three anonymous reviewers for insightful suggestions. We also thank the faculty who helped evaluate the CDCI and/or administered it to their classes.