How It’s Counted Counts

January 8, 2011

An article in the New York Times reports a small, but significant change in the way that the Advanced Placement [AP] exams will be scored.  These exams, administered every spring by the College Board, typically consist of several sections, containing multiple-choice, essay, and free response questions.  Up to now, the score for the multiple-choice section of the exam has been calculated as the number of right answers, minus a fraction of the wrong answers.  This scoring method is also used for the Scholastic Aptitude Test [SAT], also administered by the College Board.

The intent of this method was to make mere guessing unprofitable, by making the expected score from guessing zero.  For example, if there are five possible responses to each of N questions, and the test taker just guesses answers randomly, we would expect on average that (s)he would get N/5 correct, and 4N/5 incorrect.  If one point is awarded for a correct answer, and 1/4 point deducted for each incorrect answer, then on average the score will be zero.

Beginning with the 2011 tests, though, this method will be dropped for the AP Exams, and the multiple choice score will be just the number of correct answers, with no penalty for wrong answers.  (The SAT scoring method will not change.)   The apparent motivation is to make year to year comparisons easier as new AP Exams, now in the works, are introduced.

This change points up an important tip for test takers: you should always try to learn how a multiple choice test will be scored.  If only correct answers count, then it is to your advantage to answer, guessing if necessary,  every question.  If there is a penalty for wrong answers, don’t bother.

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