Twenty-three Stanford University students have been accused of cheating on computer-scored tests in a psychology course and could face a number of penalties, including expulsion. University officials said they discovered the problem by analyzing the multiple-choice tests after a graduate teaching assistant discovered two identical tests from students who shared the same house. Stanford officials are not releasing the names of the students being investigated. The allegations are being investigated by the university judicial affairs officer. If they are proved true, the students could lose credit for the course, be suspended from school or be expelled, officials said.