3: A market research firm is interested in estimating the average annual expenditure on advertising in the fundraising industry. In a pilot study, a random sample of 121 charities was chosen. The mean annual expenditure was found to be $7550 with a standard deviation of $175. Assume that the distribution of advertising expenditures across different firms in the industry is normally distributed. A) On the basis of the pilot study, determine a 90% confidence interval for u, the actual mean annual expenditure on advertising. B) The marketing firm wants its results to be accurate within $35 with 95% confidence. How large a sample size does the firm need to take? (Must use Z, not t. This will be fine as long a n is greater than 30.) Question 4 A random sample of 16 observations from an approximately normally distributed population is as follows: [15, 28, 33, 4, 14, 20, 36, 42, 19, 21, 38, 44, 19, 25, 34, 471. A) Construct a 90% confidence interval for the population variance. B) Construct a 90% confidence interval for the population standard deviation. Question 5: For a random variable x', which has chi-square distribution with 18 degrees of freedom, determine the