Question: The manufacturer of a propellant systems used in aircraft emergency escape, would like to say that his project has an average rate of combustion of 49.5 inches per minute. It assumes that the combustion rate is normally distributed. He try 20 grains of propellant selected randomly. If the average is located within an interval with a probability of 90% is satisfied.
A conclusion that comes with the following observations?

49.02 49.91 50.84 48.05 50.03 49.83 51.19 49.08 50.25 50.31 50.24 49.23 49.20 49.88 49.78 50.64 49.74 49.51 50.76 50.17
Combustion rate (in / min)