Go through the questions in attachment. (4 short questions)

One of them is shown below

2. Suppose I wanted to know whether a surprise quiz before the midterm improves your midterm score. Since I’m teaching two sections of this class, I decide to test this by setting a surprise quiz for the first section and not for the second section, and then comparing the average scores of the two sections on the midterm. What assumption(s) would need to hold in order for me to estimate the true effect of a surprise quiz on midterm score in this manner? Explain.