The mean score for freshman on an aptitude test at a certain college is 800 with a standard deviation of 50. That is the probability that two groups of students selected at random, consisting of 36 and 49 students, respectively, will differ in their mean scores by: (Assume mean scores are continuous)
a) more than 12 points?
b) an amount between 7 and 15 points?
The professor listed the answers to be:
a) 13.7%
b) 17.6%