Many colleges and universities have adopted the student ratings of instruction (SROI) system as one of the measures for instructional effectiveness. This study aims to establish a predictive model and address two questions related to SROI: firstly, whether gender bias against female instructors at North Dakota State University (NDSU) exists and, secondly, how other factors related to students, instructors and courses affect the SROI. In total, 30,303 SROI from seven colleges at NDSU for the 2013-2014 academic year are studied. Our results demonstrate that there is a significant association between students’ gender and instructors’ gender in the rating scores. Therefore, we cannot determine how the gender of an instructor effects the course rating unless we know the composition of genders of students in that class. Predictive proportional odds models for the students’ ordinal categorical ratings are established.