Causal Diagrams for Descriptive Statistics

Without random sampling and/or random allocation, even descriptive statistics such as simple means or proportions can be quite misleading. Therefore, causal diagrams were added to existing course materials to address this topic and to illustrate the differences between random and convenience samples and between observational and experimental studies. We assessed student understanding in different courses with a pre-/post-survey. Additionally, we asked students to evaluate the helpfulness of the diagrams for their understanding. There is a statistically discernible positive effect with 280 students from more than seven different courses on pre- to post-knowledge. Also, most of the students agreed with the statement that the causal diagrams helped in their understanding.