Vol. 8, No. 4

April 2006

PQ Systems

Software support options

Quality Quiz: With a video!

Six Sigma

Data in everyday life

Bytes and pieces

FYI: Current releases


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Quality Quiz:

Click here for a more complete video explanation

Walker Runn is quality manager for Color in a Can, a paint processing company with facilities in three states. He is pleased to be assigned to the plant that lies furthest from company headquarters, hoping that an "out of sight, out of mind" sensibility will keep the home office from pestering him about things like statistical process control, or getting more training to do his work, or a host of other things that are pebbles in his shoe.

The company sends a vice president to audit his quality systems each year, but Walker has been able to sustain a facade of competence because the vice presidents that the home office sends have generally known little about statistical process control, so he can simply throw around a few impressive terms and charts and they leave satisfied. This time, however, the company has chosen to send Dan Druff, a highly competent (though somewhat flaky) statistician.

Thumbing through an old statistics textbook, Walker Runn decides that the only way to convince Dan Druff that the plant is producing consistently high quality paint, is to wow him with hypothesis testing. Since he has never done hypothesis testing himself, Walker finds that he must actually skim the chapter to learn some terminology. A section entitled "Differences between Means" draws his interest. In the associated case study, a plant has two identical production lines that produce identical products--not unlike the way Color in a Can is set up, with two lines that produce the same product.

As part of the corporate quality effort, each production line is rated on a quality index each day. Data for the two lines follows:

Walker collects the data below and asks one of his employees to enter it into a statistical software program so it can be presented to Dan Druff in a Major PowerPoint presentation that he has planned.

As he shares the presentation, he points to the high t value of 2.834. "Aha," he says. This demonstarates how different the lines are from each other, he points out to Dan Druff, who nods, and then asks Walker what alpha value might be used.

Oh-oh. "Selecting the Alpha" was in the part of the chapter that Walker had not skimmed. The only connection with 'alpha' that came to his mind derived from the sports car his neighbor just bought, an Alfa Romeo 164. Fishing for a response, he blurted out "12," since the sum of and is 12. Not fancy, but a fast calculation, he thought to himself.

Note: I am his neighbor. This is my Alfa Romeo 164. (What do you think of my license plate?)

Was Dan Druff impressed? Should he have been?

a) No. Walker Runn should have done more than brush up on his terms.

b) Yes. Dan Druff went back to company headquarters praising Walker Runn's grasp of statistical quality control as well as the plant's production process.

Copyright 2006 PQ Systems.
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