Question: The army reports that the distribution of head circumference among male soldiers is approximately Normal with mean 22.8 inches and standard deviation 1.1 inches.
(a) A male soldier whose head circumference is 23.9 inches would be at what percentile? Show your method clearly.
(b) The army's helmet supplier regularly stocks helmets that fit male soldiers with head circumferences between 20 and 26 inches. Anyone with a head circumference outside that interval requires a customized helmet order. What percent of male soldiers require custom helmets?
(c) Find the interquartile range for the distribution of head circumference among male soldiers.