Suppose your ECO 3150 professor informs you that on the final examination two students received grades of 80 and 50 respectively, and that the standardized scores corresponding to those grades are 1 and -1, respectively.
(i) What is the mean and standard deviation of the scores on the final examination for ECO 3150 students?
(ii) If the scores are approximately normally distributed, what proportion of students should lie between 45 and 90?