Solutions Operations management

Solution) You are in charge of creating a control chart for your new process. You take 25 samples of n=4 each.

Question: You are in charge of creating a control chart for your new process. You take 25 samples of n=4 each. The data is shown below.

x1	x2	x3	x4
59.7	58.7	60.2	61.3
61.2	61.7	57.8	59.8
61.1	58.9	59.3	58.3
58.2	59	59.2	57.9
59.4	59.6	60.1	59.6
59.7	59.6	61.3	59.9
59.8	59.5	62	60.9
62.4	59.3	61.7	58.4
60.5	60.9	61.9	59.9
59.5	60.7	59.6	60.8
58.6	59.2	58.5	59.6
60	60	59.7	62.2
58.3	59.3	57.4	61.4
58.7	59.3	60.8	60.5
60.9	60.6	58.6	58.9
60.7	60.3	59.1	59.8
60.1	60.6	60.1	59.1
61.9	60.5	60.1	60.8
60.9	59.4	59.1	61.1
58.8	58.4	60.7	60.6
62.2	61.4	61.3	60.1
60	60.5	60	58.9
58.2	60.8	60.4	60.6
60.2	59	61.2	59.7
59.2	59.2	59.6	59.5

a. Using the "Rbar" method for estimating the standard deviation, make an xbar and R chart. You may use Excel or Minitab, but you must show how the control limits are calculated.

b. You decide to accept the control limits and go to phase II. The next 5 samples are shown below. Add them to your control chart. Is your process still in control? If not, what has changed? Based on the results, what do you recommend?