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Statistical Process Control for Richardo's Widgets

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Ricardo's Widgets makes a critical part for a popular brand of cell phones. Consider the data for 15 samples of size 4 of a key dimension for the part, show in the worksheet. Specifications are 0.110 +/- 0.015.

a. Compute control limits for an x-chart using the statistic R/d2 as an estimate of the standard deviation and using the actual standard deviation for the data. Why are they different?

b. Construct the x- and R-charts and an x-chart for the 'individuals' using the data. Interpret the results.

c. Estimate the process capability by using the actual sample standard deviation.


Solution Summary

The solution is an annotated Word doc and Excel spreadsheet.