Not exactly. There is no target average. However, I do check for questions that more than 2/3 of you missed. The number of such "hard" questions is subtracted from the total number of questions on the exam to get the effective number of questions. To calculate your score, I divide the number you got right by the effective number of questions. If that gives you a score over 100%, I drop it to 100%.

The "hard" questions are usually good questions, so I want to give credit to those who got them right. I do not let your exam score go over 100%, so you do not get "extra credit." However, getting a "hard" question right means that you can miss one of the other questions without penalty.