Number in Class: 152. The entering class size is 152, which includes 5 positions for the MD/PhD (MSTP) program, leaving 147 for the general MD. The MD class is made up of 70% Iowa residents. The MSTP does not have a residency requirement. About the SDN Ranking. SDN Ranking identifies how SDN members perceive the quality of a school relative to other schools of the same type (e.g., other Medical Schools, other Dental schools, etc.). Schools are ranked from 1, perceived as much worse than other schools, to 5, perceived as much better than other schools..