1. Suppose that scores on the Math SAT exam follow a Normal distribution with mean 500 and standard deviation 100. Two students that have taken the exam are selected at random. What is the probability that the sum of their scores exceeds 1200?
A. 0.1587
B. (0.1587)2
C. 0.0793
2. There are twenty multiple-choice questions on an exam, each having responses a, b, c, or d. Each question is worth 5 points and only one response per question is correct. Suppose a student guesses the answer to each question, and her guesses from question to question are independent. The student's mean score on the exam should be
A. 5.
B. 25.
C. 50.
3. The scores of individual students on the American College Testing (ACT) Program College Entrance Exam have a normal distribution with mean 18.6 and standard deviation 6.0. At Westside High, 400 students take the test. Assume their scores are all independent. If the scores at this school have the same distribution as nationally, the probability that the average of the scores of all 400 students exceeds 19.0 is
A. the same as the probability that a single student has a score exceeding 19.0.
B. larger than the probability that a single student has a score exceeding 19.0.
C. smaller than the probability that a single student has a score exceeding 19.0.