The vast majority of tests we give are multiple choice. We don't have Scantron, so instructors grade these by hand. Since each test is usually 10 or 20 questions and the answer sheets are in columns of 5, grading tests by pattern recognition becomes very easy. Comparison of the pattern on the student's answer sheet to a master key allows instructors to mark wrong answers from top to bottom of the sheet, not from question 1 through 10 or 20. Using this system is quick and effective, and becomes a huge time saver. Another time saver in grading multiple choice tests is to have an answer sheet with the correct answers hole-punched out of it. Simply marking the student's sheet where there is no answer seen in the hole allows rapid, accurate grading.