Decide whether the normal model is applicable
The histogram below summarises readings from a calibrated pressure gauge during repeated checks, measured in kPa. There are 55 observations. The bins and frequencies, in order, are 120–140: 6; 140–160: 9; 160–180: 12; 180–200: 10; 200–220: 8; 220–240: 6; 240–260: 4