CarPro specializes in renting cars for students going on spring break. Due to the long travel distances, the company carefully controls the miles-per-gallon that the cars get. Sample data are given below. The process standard deviation is not known. Construct an X-bar and R-chart with the data.
Observation
Sample 1 2 3
1 20.4 20.2 21.4
2 19.3 20.5 20.8
3 21.1 20.8 20.1
4 21.1 19.7 20.5
5 20.1 21.1 19.5
