Unoccupied seats on flights cause airlines to lose revenue. A large airline wants to estimate its average number of unoccupied seats per flight over the past year. To accomplish this, the records of 225 flights are randomly selected, and the number of unoccupied seats is noted for each of the sampled flights. The summary statistics for the number number of unoccupied seats for the 225 flights was: sample mean 11.6, and standard deviation 4.1 (t* = 1.97).
