One reason why you may be motivated to write a textbook is that you don't consider existing ones appropriate for one of your courses. If this was your reason for authoring a textbook, you would be likely to use it. While you may be confident that doing so is both ethical and appropriate educationally, you may wonder whether it is likely to affect your student ratings, and if so, how.

We recently gathered some data on these concerns. We had 50 Marquette University students rate 17, seven-point semantic differential scales. Each student was randomly assigned to one of two groups. Twenty-five rated "A Professor" on the scales, and 25 rated "A Professor Who Uses His/Her Own Textbook" on them. The scales, which were constructed from adjectives on the course rating form used at Marquette, were the following: understandable/hard to understand, well prepared/not well prepared, effective/ineffective, competent/incompetent, good sense of humor/poor sense of humor, unbiased/biased, confident/nervous, stimulating/boring, friendly/unfriendly, warm/cold, interesting/boring, industrious/lazy, realistic/unrealistic, approachable/unapproachable, superior/inferior, trustworthy/untrustworthy, and reliable/unreliable. The mean of the ratings for each scale for each group was computed. The mean of the 17 mean ratings for each group was also computed.

Fortunately, these data indicate that using a textbook you authored is likely to adversely affect your student ratings little, if at all. The means of the ratings for 12 of the scales were almost identical and the differences between groups for four of the remaining five scales were very small.

A professor who uses his/her own textbook was judged to be somewhat less well prepared and a little more boring, trustworthy, and reliable than one who doesn't. The only scale on which there was a substantial difference between groups was unbiased/biased. A professor who uses his/her own textbook was judged to be more biased than one who doesn't. Consequently, you would be wise to go out of your way to convince students that your reason for using your own book is not bias. The means of the 17 mean ratings for the two groups were identical.