Unoccupied seats on flights mean lost revenue for airlines. A large airline wants to estimate its mean number of unoccupied seats per flight over the last year. The airline takes a random sample of 225 flights and calculates the average number of unoccupied seats to be 11.6 Assume the population standard deviation of unoccupied seats for all flights for this airline is equal to 4.103
a) Find a 90% confidence interval for μ and the mean number of unoccupied seats
b) Suppose the company wants their 90% confidence interval to have a margin of error of no more than 0.25. How large must the sample size be to satisfy this requirement?