It’s hard to determine just how well students understand the concepts we teach. Our usual criterion for understanding is that students give a correct answer on an exam, but that leaves much to be desired (Uminski et al., 2024). In multiple-choice exams, the student may select the correct alternative, but that doesn’t mean they understand why that answer is correct, whether they used correct reasoning to get it, or whether they know in what ways the correct alternative is better than the others. Some people believe that essay exams are better at revealing understanding, but that isn’t necessarily the case. Students can give memorized answers that they don’t really understand, or they can write scattershot essays with a lot of facts, hoping that some part will score points. It is challenging to design an assessment, formative or summative, that reveals individual student understanding, especially within the time constraints of a class period.
