(a) 15 samples of n = 8 have been taken from a cleaning operation. The average sample range for the 20 samples was 0.016 minute, and the average mean was 3 minutes. Determine the three- sigma control limits for this process.
(b) 15 samples of n = 10 observations have been taken from a milling process. The average sample range is 0.01 centimetres. Determine upper and lower control limits for sample ranges.
(c) Determine which of these three processes are capable:
Process Mean Standard Deviation Lower Specification Upper Specification
1 6.0 0.14 5.5 6.7
2 7.5 0.10 7.0 8.0
3 4.6 0.12 4.3 4.9