A professor found out from a senior professor that engineering students in Harp University tend to do good in their Engineering Management subject, claiming that historically, the mean grade of...

A professor found out from a senior professor that engineering students in Harp University tend to do good in their Engineering Management subject, claiming that historically, the mean grade of engineering students in the said course is 1.50. Curious if this claim was true, the professor took a random sample of 9 students who took the engineering management subject. Before collecting data, he was undecided about his own claim because he knew of some students who did really good in the course but has also encountered others who did poorly. He found that their mean grade for the course is 1.35 with a standard deviation of 0.50. Use the Test of Significance Approach in testing the professor’s claim. a. Estimate population mean at 90% confidence interval. b. Between z and t, which is more appropriate to use given the data? Why? c. What are the chances that your estimate of population mean was wrong? Describe and explain a potential source of error to your estimate. d. Holding % of CI constant, what can you do to lower your chances of error? Why? Note: show solutions. need answer asap. will give a good feedback right away as well.