Scenario: We will continue to examine the World Development Indicators data in BirthRate 2017. Throughout the exercise, we will use BirthRate as the Y variable. We will broaden our analysis to work with other variables in that file:

a. Earlier, we estimated a quadratic model with maternal mortality as the independent variable. To that model, add the categorical variable MatLeave90+, which indicates whether there is a national policy to provide 90 days or more maternity leave. Evaluate your model and report on your findings.

b. Investigate whether there is any interaction between the maternity leave dummy and the rate of maternal mortality. Report on your findings, comparing these results to those we obtained by using the model without the categorical variable.