Sample Means and Ranges Were Obtained for Five Samples of 10

Multiple Choice

Sample means and ranges were obtained for five samples of 10 units per sample from a production process. Assume the process was considered to be in control during the period these samples were collected. The results are as follows:

LCL for the three sigma X chart for the process is approximately (for a sample size of 10, A₂ = 0.31) :

A) 10.12.
B) 10.05.
C) 10.94.
D) 9.44.
E) 9.75.