Many measurement biases affect student evaluations of instruction (SEIs). However, two have been relatively understudied: halo effects and ceiling/floor effects. This study examined these effects in two ways. To examine the halo effect, using a videotaped lecture, we manipulated specific teacher behaviors to be "good" or "bad" based on specific items on the evaluation form (the Teacher Behavior Checklist). To examine ceiling/floor effects, we expanded the standard 5-point rating to either 7 or 9 points. Across three universities, 537 students watched and rated the videotaped lecture. Both biases were robust and remained despite characteristics of the measure designed to combat them. Instead, direct instruction regarding how to use the evaluation forms seems to be necessary to limit these biases on ratings. (Contains 3 figures and 5 tables.)