Demonstrates heteroscedascity, and shows how the presence of heteroscedascity means that a misspecification has taken place, which may be in terms of a missing interaction effect. The data contains 4 variables cash is the amount of money that an individual earns, import is the importance of the work that a particular charity does, to that person, and given is the amount of money that individual donated to the charity. The dataset also includes a variable di_cash, a dichotomised cash variable, to enable the interaction to be explored.