A university department is interested in the effectiveness of providing drop-in statistics classes for first year students. They carry out a randomised encouragement study in a large introductory statistics class. At the start of term, students are randomised to either receive an email welcoming them to the class and encouraging them to attend additional drop-in support sessions, or just receive an email welcoming them to the class. Attendance of the drop-in support classes is recorded. All students are able to attend the drop in classes, but the students who didn’t get the encouragement email would need to find out about them via other sources.The outcome is the final exam mark
Draw a DAG representing plausible causal relationships in this study. Write down the treatment, the outcome and the instrumental variable