Process time at a workstation is monitored using sample mean and range control charts. Six samples of n = 9 observations have been obtained and the sample means and ranges computed (in minutes): Sample Mean Range 1 3.28 0.42 2 3.29 0.44 3 3.16 0.45 4 3.20 0.43 5 3.30 0.50 6 3.06 0.44