3.19 A film-processing shop promises to deliver photographs in half an hour. The mean and standard deviations of the processing times are 22 minutes and 3 minutes respectively.

The layout of the machines in the shop has been altered. The processing times of the first ten films to be developed after the reorganization are 32.6 28.2 30.8 28.1 27.0 25.1 23.2 32.5 24.9 32.8 Plot a control chart and use it to ascertain whether the reorganization has affected the processing times