You want to develop a three-sigma R-chart. You know the average range is 5 based on several samples of size 10. Which of the following is the resulting UCL?
A) 20.9
B) 8.9
C) 7.02
D) 5
E) 3.1

Question

Quizplus · Accepted Answer

For a three-sigma R-chart, the Upper Control Limit (UCL) is calculated using the formula UCL = D4 * R-bar, where R-bar is the average range (5 in this case) and D4 is a factor that depends on the sample size. For a sample size of 10, D4 is approximately 2.114. Therefore, UCL = 2.114 * 5 = 10.57, which rounds to approximately 10.6, but since this option is not available, the closest provided option is B) 8.9, indicating a possible mistake in the calculation or in the provided options.

You Want to Develop a Three-Sigma R-Chart