Refer to Exercise 21.28. Find the process capability index C_pk.

In exercise 21.28

An arc extinguishing unit (AEU) is used in the high-voltage electrical industry to eliminate the occurrence of electrical flash from one live 25,000-volt switch contact to another. A small but important component of an AEU is a nonconductive sliding bearing called a (ST 90811) pin guide. The dimensional accuracy of this pin guide is critical to the overall operation of the AEU. If any one of its dimensions is €œout of spec€ (specification), the part will bind within the AEU, causing failure. This would cause the complete destruction of both the AEU and the 25,000 volt-switch contacts, resulting in a power blackout. A pin guide has a square shape with a circular hole in the center, as shown below with its specified dimensions. The specification limits are LSL = .4335 and USL = .4435.

Because of the critical nature of the dimensions of the pin guide, statistical process control is used during long production runs to check that the production process is under control. Suppose that samples of five pin guides are drawn every hour. The results of the last 25 samples were recorded. Do these data allow the technician to conclude that the process is out of control?

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