Airplane manufacturers use only slow-burning materials. For the plastic in coffee pots the maximum burn rate is 4 inches per minute. An engineer at Hawker-Beechcraft randomly sampled from a case of 120 Krups coffee pots and obtained burn rates of 1.20, 1.10, and 1.30 inches per minute.
Calculate a 99.9 percent confidence interval and write an interpretation that tells about using Krups coffee makers in airplanes.