A common concern is that students will rate classes poorly if they are challenging, and rate classes higher if they think they’ll do better. Marsh (1987) found that a majority of instructors believe that difficulty, workload, and stringency of grading all negatively bias student ratings. Stroebe (2016) argues that the valuing of SETs has led to grade inflation based on studies that show expected grades correlate with student ratings, examined using manipulated grades. However, when real grades and student grade expectations are compared, Centra (2003) found that expected grades don’t affect SETs. Regarding course difficulty, Centra found there is a middle ground for class difficulty. Classes that were not only too difficult, but also ones that were too easy, received lower ratings than classes that found an appropriate balance.