Muddiest Point
According to Angelo and Cross (1993), the Muddiest Point is one of the easiest methods of formative assessment. In order to employ this technique, the instructor simply asks students to complete the following question: "What is the muddiest point in [X]?" In this technique, [X] may be a lecture, a reading, a discussion, a set of exercises, or almost any other learning experience. Obviously, this is one of the more subjective formative assessment methods, as it is not testing student knowledge so much as it is asking what aspect of their recent learning experience they are the least confident about. However, that subjectivity is also what makes this such a quick and focused technique. This technique is also appealing to students who are hesitant to speak up in class, especially when acknowledging they don't understand something. This technique can be easily employed in an anonymous way, which often empowers shyer students.
As with many formative assessments, the Muddiest Point can be adapted to meet the needs and preferences of the faculty employing it. Students can be asked to write the muddiest point on a piece of paper or an index card, or they can post it to a web tool like Google Slides.
References
Angelo, T. A., & Cross, K. P. (1993). Classroom assessment techniques: A handbook for college teachers. San Francisco: Jossey-Bass Publishers.
Assessing Student Learning | Formative Assessment | Summative Assessment