This appendix provides some typical formulas used in the control charting process. The list by no means is an exhaustive one; however, it provides the quality professional with some basic approaches to statistical understanding for the everyday application of some common charts. Specifically, the reader will find some explanation of the "average" calculation, the sequence of calculating control limits of selected variable and attribute charts , hints about using a typical calculator, and a list of the most common formulas used in pursuit of SPC.
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Condition | Test for Normality | Test for Exponentiality | Remarks |
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n ‰ 8 and n ‰ 25 |
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n > 25 and n < 125 |
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| Chi-Square goodness-of-fit test
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n ‰ 125 |
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Note: Not recommended: (1) Kolmogorow-Smirnov; (2) standard chi-square goodness-of-fit test over pretabulated data. |