Section 3 Control Charts
Lesson S03-04
Text: Section 3 pages 20 & Section 9 pages 6 – 9
Duration: 22 minutes
Minitab demonstration on creating control charts
Introduction to Exercise 3 and 4
Exercise 3 is optional yet is good practice.
Exercise 3
30 samples of size 4 (n = 4) have been collected. The average of the averages is 130mm. The average range is 10mm.
a. What are the control limits for the XÌ„ chart?
(Hint: use the worksheet for X̄ and R chart calculations. Download the  X̄ and R Charts Calculations Worksheet and graph paper. Or view workbook pages Section 3: Page 11 and 12.)
b. What are the control limits for the R chart?
Solution / Discussion of Exercise 3
Exercise 4
A Key Characteristic of an O-Ring is the Radial Cross Section. 26 samples of size n=5 were taken. The data is shown below and may be found in the file Exercise04.MTW
a. Construct XÌ„ and R Charts (or XÌ„ and S Charts) and assess the process stability.
Solution / Discussion of Exercise 4 a
b. Assume that the out of control point in the chart constructed above is a Type I Error (the process is actually stable) and answer the following questions.
What is the estimated process average?
What are the control limits for the XÌ„ Chart?
What is the average Range?
What are the control limits for the Range chart?
Leave a Reply