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Question: as part of the process for improving the quality of...

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As part of the process for improving the quality of their cars, Toyota engineers have identified a potential improvement to the process that makes a washer that is used in the accelerator assembly. The tolerances on the thickness of the washer are fairly large since the fit can be loose, but if it does happen to get too large, it can cause the accelerator to bind and create a potential problem for the driver. (Note: This part of the case has been fabricated for teaching purposes, and none of these data were obtained from Toyota.) Let’s assume that, as a first step to improving the process, a sample of 40 washers coming from the machine that produces the washers was taken and the thickness measured in millimeters. The following table has the measurements from the sample:

1.9 2.0 1.9 1.8 2.2 1.7 2.0 1.9 1.7 1.8
1.8 2.2 2.1 2.2 1.9 1.8 2.1 1.6 1.8 1.6
2.1 2.4 2.2 2.1 2.1 2.0 1.8 1.7 1.9 1.9
2.1 2.0 2.4 1.7 2.2 2.0 1.6 2.0 2.1 2.2

Upper thickness limit is 2.4 and Lower thickness limit is 1.4


1. Set up X - and range control charts for the current process. Assume the operators will take samples of 10 washers at a time.

2. Plot the data on your control charts. Does the current process appear to be in control?

3. If the process could be improved so that the standard deviation was only about .10 millimeter, what would be the best that could be expected with the

processes relative to fraction defective?

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