An achievement test measures what a student has learned in a particular subject area over a period of time. It focuses on how much a student knows about specific topics like math, science, or geography. Achievement tests are used to determine if students should advance to the next grade, motivate students before a new assignment, and identify what topics students have mastered or are still struggling with. A good achievement test is reliable, valid, easy to administer, inexpensive, and has questions that are neither too easy nor too difficult for students. It also allocates sufficient but not excessive time for students to complete.