Statistical Methods for Six Sigma (In R&D and Manufacturing) || Other Useful Charts

✍ Scribed by Joglekar, Anand M.

• Publisher: John Wiley & Sons, Inc.
• Year: 2004
• Tongue: English
• Weight: 244 KB
• Edition: 1
• Category: Article
• ISBN: 0471203424
• DOI: 10.1002/0471721212.ch6

✦ Synopsis

A control chart is a way of monitoring, controlling, and improving a process; i.e., a way of managing a process. This process management involves risks-the risk of false alarm and the risk of not detecting a process shift when it has occurred. It also entails costs, such as the cost of off-target products, the cost of sampling, and the cost of corrective action. At times, it involves special circumstances not considered by the traditional variable and attribute control charts discussed in Chapter 4. This chapter considers five additional control charts: risk-based charts, modified limit charts, charts to detect small shifts, short-run charts, and charts for nonnormal distributions. These charts are useful in many practical applications. Risk-based charts explicitly manage the two risks of making wrong decisions. Modified limit charts are useful when it becomes uneconomical to adjust the process every time it goes out of control. Such is the case when the process capability is high and the cost of adjustment is also high. Charts to detect small shifts are useful when it is important to rapidly detect small but sustained shifts, as would be the case when process capability is low. Short-run charts deal with the situation in which the same process is used to produce multiple products, each for a short period of time. In this case, keeping a separate chart for each product becomes ineffective and inefficient. Charts for nonnormal distributions apply when the distribution of the plotted point departs significantly from a normal distribution. 6 Other Useful Charts 153 Statistical Methods for Six Sigma by Anand M. Joglekar