Statistical Sciences 2141A/B Lecture Notes - Lecture 34: Standard Deviation
4 Dec 2018
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Document Summary
Control charts provide a mechanism for recognizing situations where assignable causes may be adversely affecting product quality. Once a chart indicates an out-of-control situation, an investigation can be launched to identify causes and take corrective action. Consider first the case in which the values of both and are known. Suppose that at each of the time points 1, 2, 3, . , a random sample of size n is available. I q y k y b from sample data prior to determining the control limits. Denote the number of observations in each sample by n, and let k represent the number of samples available. Typical values of n are 3, 4, 5, or 6; it is recommended that k be at least 20. Assume that the k samples were gathered during a period when the process was believed to be in control k k. Traditionally, the first method was used due to its ease of calculation.
