Quality quiz (October 2017): Answer A

I’m sorry:

The correct answer is “B”

No. Simsack failed to tell his students about data patterns that indicate out-of-control situations even when data falls within control limits. The pattern reflected in this chart is statistically impossible if the process is truly in control. The sample p’s will form a normal distribution when the process is in control. But this chart reflects a number of points near the control limits and none around the average:

But virtually all of the points lie in the outer band—a pattern that could be caused by a variety of conditions, including some magic pencil that keeps things from getting out of control.

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