The College Board reported the following mean scores for the three parts of the SAT (The World Almanac, 2009): Critical reading 502 Mathematics 515 Writing 494 Assume that the population standard deviation on each part of the test is 100.

a) What is the probability that a random sample of 90 test takers will provide a sample mean test score within 10 points of the population mean of 502 on the Critical reading part of the test? (4 marks)

b) What is the probability that a random sample of 90 test takers will provide a sample mean test score within 10 points of the population mean of 515 on the Mathematics part of the test? Compare this probability to the value computed in part (a).