University of Waterloo (Canada) statistician S.H.

Stciner applied control chart methodology to the manufacturing of a horseshoe-shaped metal fastener called a robotics clamp (Applied Statistics, Vol. 47,1998). Users of the clamp were concerned with the width of the gap between the two ends of the fastener. Their preferred target width is .054 inches. An optical measuring device was used to measure the gap width of the fastener during the manufacturing process. The manufacturer sampled five finished clamps every fifteen minutes throughout its 16-hour daily production schedule and optically measured the gap. Data for four consecutive hours of production are presented in the table below.

a. Construct an ?-chart from these data.

b. Apply the pattern-analysis rules to the control chart.
Docs your analysis suggest that special causes of variation are present in the clamp manulacturing process?
Which of the six rules led you to your conclusion?

c. Should the control limits be used to monitor future process output'? Explain.

ll.17 A pharmaceutical company produces vials filled with morphine (Communications in Statktics, Vol. 27, 1998).
Most of the time the filling process remains stable, but once in a while the mean value shifts off the target of 52.00 grams. To monitor the process, one sample of size 3 is drawn from the process every 27 minutes. Measurements for 20 consecutive samples are shown in the table.

a. Construct an i-chart for these data.

b. What does the i-chart suggest about the stability of the process?

c. Is the process influenced by both common and special causes of variation? Explain.

d. Should the control limits and centerline of the ichart of part a be used to monitor future output of the morphine filling process? Explain.