According to Centra (2003), “Bias exists when a student, teacher, or course characteristic affects the evaluations made, either positively or negatively, but is unrelated to any criteria of good teaching, such as increased student learning.”
Many factors can negatively affect course ratings, including: class enrollment, physical space, first time teaching a course, first time teaching at all, preparation time (or lack thereof), trying a new teaching strategy, changing teaching methods or assignments, the level of the class, required courses vs. electives, and amount of teaching assistant support. Positive factors include seniority of the instructor, instructor rapport, student motivation and preparation, class size, level of the course within the major, and discipline, with humanities courses often rating more favorably than those in math and science classes.
Bias is not monolithic. It is essential to consider if the bias is widespread and strong enough to overwhelm the students’ ratings of the faculty member’s teaching or course environment to reflect that bias (Linse, 2017).