Quality Quiz:

“Hmm, I get it,” says Marsha Mallow to her colleague.

Maura Thesame responds: “You mean about recognizing out-of-control?”

The two had wandered down the path of chart interpretation, finally reaching the point of understanding that a point above or below control limits might signal an out-of-control situation.

Feeling smug about their progress on the learning curve, the two were congratulating each other when a technician brought a chart from butter packaging line #2 with a series of averages (X-bar) above the grand average ( X-double bar).

The technician thinks that something is wrong, and wonders if he should do anything about the process. Since all the points are within control limits, Marsha Mallow points out," the process is certainly in control, so it doesn’t need any action,” Maura Thesame finishes her sentence.

Is this a stable process?

a) Yes. Control limits clearly indicate the point at which the process is deemed out of control, and these are within those limits.

b) No. The technician's instincts are correct. The process is not stable.

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