1. A random sample of 87 airline pilots had an average yearly income of $99,400 with a standard deviation of $12,000. If we want to determine a 95% confidence interval for the yearly income, what is the value of t? b. Develop a 95% confidence interval for the average yearly income of all pilots. a. average 2. A sample of 144 cans of coffee showed an average weight of 16 ounces. The standard deviation of the population is known to be 1.4 ounces. Construct a 68.26% confidence interval for the mean of the population. 3. A researcher is interested in determining the average number of years employees of a company stay with the company. If past information showvs a standard deviation of 7 months, what size sample should be taken so that at 95% confidence the margin of error will be 2 months or less?