Suppose that you are asked to investigate the hypothesis that a grade on a final exam in Econ 227 (grade) depends on classes attended (att). The data come from ECON 227 class for the fall 2019 semester.

(a)What economic data sets (time series vs. cross sectional) are you going to collect to analyze your empirical model? And explain why?

(b)Explain the zero conditional mean assumption using this model.