Raytheon of Canada Limited produces printed circuit boards (PCBs), which involve a number of soldering operations. At the end of the process, the PCBs are tested to determine whether they work properly. There are several causes of PCB failure, including bad flux, improper heating, and impurities. A reject rate of less than .80% is considered acceptable. Statistical process control is used by Raytheon to constantly  heck quality. Every hour, 500 PCBs are tested. The number of defective PCBs for the past 25 hours is shown here. Draw a p chart and apply the pattern tests to determine whether the process is under control.

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