A Computer Program to Calculate Two-Stage Short-Run Control Chart Factors for (X¯, s) Charts

ABSTRACT

This paper describes the development and execution of a computer program that will accurately calculate first- and second-stage short-run control chart factors for (X¯, s) charts. The software used is Mathcad 8.03 Professional with the Numerical Recipes Extension Pack. The program accepts values for subgroup size, number of subgroups, α for the X¯ chart, and α for the s chart both above the upper control limit and below the lower control limit. Tables are generated for specific values of these inputs. Implications of these tabulated results are discussed. A numerical example illustrates the use of the program. Download instructions for the program are available at http://program.20m.com.

Keywords:

• Control chart
• Short-run statistical process control
• Two-stage control charting
• Distribution of the standard deviation
• Distribution of the studentized standard deviation
• Distribution of the mean standard deviation.