Table 6.1 Factors for Calculating Three-Sigma Limits for the -Chart and -Chart

Multiple Choice

Table 6.1
Factors for Calculating Three-Sigma Limits for the -chart and R-chart
Source: 1950 Manual on Quality Control of Materials,copyright
American Society for Testing Materials.Reprinted with permission.
-A milling operation has historically produced an average thickness of 0.005 inch with an average range of 0.0015 inch.Currently,the first three items from each batch of 20 are inspected.Use Table 6.1.What is the value of LCL if the sample size is increased to 6?

A) less than or equal to 0.0030
B) greater than 0.0030 but less than or equal to 0.0049
C) greater than 0.0049 but less than or equal to 0.0069
D) greater than 0.0069