Let x represent the sat total score of an entering freshman at university x. the random variable x is known to have a n(1200, 90) distribution. let y represent the sat total score of an entering freshman at university y. the random variable y is known to have a n(1215, 110) distribution. a random sample of 100 freshmen is obtained from each university. let = the sample mean of the 100 scores from university x, and = the sample mean of the 100 scores from university y. what is the distribution of the difference in sample means between university x and university y: – ?