ABSTRACT
The Six Sigma approach, which was originally introduced by Motorola’s Government Electronics Group, has caught on quickly in the industry. Statistical process control means controlling a process statistically. Statistical process control originated from the efforts of the early quality control researchers. The statistical theory useful to generate control limits is the same for all the charts with the exception of exponential weighted moving average and cumulative sum. The range chart is a time plot useful in monitoring short-term process variations, while the X¯ chart monitors the longer term variations where the likelihood of special causes is greater over time. Each subgroup should be selected from some small period of time or small region of space or product in order to assure homogeneous conditions within the subgroup. In order to identify value-adding elements of a Lean project, the component tasks must be ranked and comparatively assessed.
