3) Estimation and Hypothesis Test (1 sample) (6 marks) The annual salaries (in dollars) for a random sample of 21 accounting executives in Toronto, Ontario are listed below: 57,860 66,863 91,982 66,979 66,940 82,976 67,073 72,006 73,496 72,972 66,169 65,983 55,646 62,758 58,012 63,756 75,536 60,403 70,445 61,507 66,555 (a) What is the best estimate of the average annual salaries? (b) Determine the 95% condence interval for the average Salaries. Interpret its meaning. (c) An Analyst claims that the mean annual Salary for advertising account executives in Toronto, Ontario is more than the national mean, $67,800. Assume the population is normally distributed and the population standard deviation is $7800. At or = 0.05, is there enough evidence to support the Analyst's claim? Answer in the following steps. (d) Which type of error (I or II) might have occurred in your decision above? Explain the error in that situation