Title: Using CUSUM Charts to Detect Small Process Shifts
Author: Keith M. Bower
Publication Source: International Society of Six Sigma Professionals, EXTRAOrdinary Sense, Vol. 2 No. 3, May 2001, pp. 1, 8
Abstract
In this article, the author investigates the use of the Cumulative Sum (CUSUM) chart, which is a useful tool to detect small but persistent changes in a process. This paper makes use of a MINITAB macro which may be downloaded for free.
Notes
The inspiration for this article was a short paper by George Box, which is available via download R170 after clicking here.
Though the CUSUM procedure is criticized by some authors as being difficult to understand, I fail to see why this is the case. When teaching, the golf scoring analogy seems to work very well.
The macro was written solely to automate the method discussed in Box’s paper and remove some of the mathematical “legwork” – though it's trivial from a mathematical perspective. Admittedly, my motivation was to encourage readers to look at Box’s paper – this article being a “first step” to it. Handily, it's available online (as discussed above) via download R170 after clicking here.
To download Adobe Acrobat (for free) click here.