An alternative to the p chart for the fraction defective is the np chart for number defective.

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An alternative to the p chart for the fraction defective is the np chart for number defective. This chart has UCL = np̅ + 3 √np̅(1-p̅) , LCL = np̅ - 3√np̅(1-p̅), and the number of defectives from each sample is plotted on the chart. Construct such a chart for the data of Example 16.6. Will the use of an np chart always give the same message as the use of a p chart (i.e., are the two charts equivalent)?
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