>(snipped) >2. If their were no penality then, in your example, 20 MC each with five >choices, you guess on all and you get 4 correct your score is 4. Using the >penality formula your score is 0, zip, nada. So guessing at random will not >help or hurt you.
I disagree. The PROBABILITY is that "guessing at random will not help or hurt you", but we all know that probability is not a guarantee. For thousands of students guessing on several questions each, the scoring scheme balances good guesses against bad, but for any INDIVIDUAL student -- unless s/he is particularly lucky (or, at least, not particularly UNlucky) guessing can significantly damage an otherwise good score. If that student could take the test over and over, then guessing makes since to me. With one shot at a performance, however, that evaluates a year's worth of work and that can be worth a college credit, I advise my students not to take the risk of guessing unless they can eliminate enough answers on a question (which is seldom the case) to swing the probability HEAVILY in their favor.
>(snipped) >Lin McMullin >Ballston Spa, NY
Wayne Murrah, Chairman, Math Dept. Porter-Gaud School 300 Albemarle Rd. Charleston, SC 29414