© 2018 E. Theobald. CBE—Life Sciences Education © 2018 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

I thank Alison Crowe, who graciously provided the data used in the extended example. Additionally, this article was greatly improved by comments from two anonymous reviewers; Erin Dolan, the editor; and several friendly reviewers, including Sarah Eddy, Ailene Ettinger, Leander Love-Anderegg, Roddy Theobald, and the members of the University of Washington Biology Education Research Group.

PDF download