We want to test if there is a difference in the number of male vs female newborns. To test our hypothesis, we pulled sex information of newborns from University of Iowa Hospitals and Clinics' electronic medical records. From July 1st, 2018, to Sept 30th, 2018, 400 babies were born and 215 of them were males and 185 of them were females. Assume two-sided type I error rate of 0.05.

a. What type of study is this?

b. What are the null and alternative hypotheses?