A professor believes that the mean mark of final exam (out of 100) of his subject is more than 60. Accordingly, he selects 100 students at random and finds that the average mark to be 63 and the standard deviation is 15. To see if his belief is substantiated, conduct the test at a suitable significant level. State the assumptions made. see if his belief is substantiated, conduct the test at a suitable significant level. State the assumptions made.