Hi Glenda, I solely agree with you, class preparation is extremely important to help avoid commonly made instructor mistakes. Students can tell very quickly when an instructor is unprepared. Unpreparedness will cause an instructor to lose credibility. We are all human, and from time to time, we as instructors may make mistakes. Own up to your mistakes and move forward. Students will have greater respect for you, if you take responsibility for your actions. I like the idea of you having the students do research to find the answer as well. I use this tactic with my students also. Patricia