Quality eLine Newsletter
November 2004
Vol. 6, No. 11

Quality Quiz

Even when she’s headed down the wrong path, Marge Orrine can be credited with steadfastness and a determination to stay the course. In her resolve to reach Black Belt status, she will stop at nothing, and forges ahead even when she does not have the right skills to bring about creditable results. Her repeated failures, it is to be noted, have resulted in acquiring many of these skills and enhancing her learning. There’s something to be said for that, even when the variability among weights of sticks of butter—the process with which she is concerned in her role as quality technician for Natural Butter Company—remains highly unpredictable.

When all else fails, she reasons, a little competition can go a long way. So Marge has decided to study which of the process lines produces the greatest amount of variation in the weights, in the hope that the Six Sigma team will be impressed with the outcome.

Line #1 produces quarter-pound sticks of butter, so Marge focuses on this line. Taking a sample of 100, she enters weight data into CHARTrunner, calculating the standard deviation as .35. For line #2 , which produces one-pound packages, Marge follows the same procedure, taking a sample of 100. The standard deviation for this line is 1.11. Her conclusion? Line #2 demands more work.

Examining the data, Marge’s supervisor, Rock DeBote, notices that the coefficient of variation appears on the CHARTrunner chart. “Will this statistic provide clues about which line would benefit most from improvement efforts?” he asks. Marge, with her usual stubborn hold on the path which she has begun, scoffs at that possibility. “The coefficient of variation is the log of the standard deviation. It has nothing to do with this situation,” she tells Rock.

Before Marge proceeds, it might be good to do a reality check. Which of the following statements is true?

a) Marge should be encouraged to forge ahead, abandoning the coefficient of variation in improving the stability of the process.

b) Marge should be derailed before she does further damage.


 

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