June 2001

Vol. 3, No. 6

Quality Quiz

Here's June's question from Professor Cleary. After you have read the question, click on the response that you think is correct. If you answer correctly, you can register to win a free copy of Quality Gamebox.

Rosa Mongthorns has assumed a new position as supervisor of quality for Light up Your Life Candles, and is eager to improve not only the quality of the firm's incoming materials but to enhance customer and supplier relations as well. She has been hired, in fact, primarily because of her cheery disposition and ability to deal smoothly with potential conflicts--which have often erupted in LUYLC's dealings with suppliers as well as customers. Rosa's bright smile masks a quivering insecurity about her own statistical knowledge and understanding of basic statistical process control tools, but she is determined to overcome this diffidence and to demonstrate to her group leader that she can improve quality by working closely with customers and suppliers.

A major customer has requested capability reports from Light Up Your Life, so Rosa has decided to make the same request of Wicked Wicks, Inc., a supplier to Light up Your Life, in order to solidify her understanding of capability analysis. After the supplier provides this analysis, Rosa tries to replicate it by using her own data. With a Cpk of 1.5, she is feeling smug about her ability to assure her customer about LUYLC's capability. However, she notices on the chart that nearly 3 percent of the data points are out of spec. After mulling over the situation and realizing that this may represent a problem, she confidently deals with it by whiting out the offending data, making a copy of the chart, and sending it on to the customer.

While no one could countenance this deceptive behavior on her part, it underlines the magnitude of her ignorance about capability, that it could bring her to actually modify the report. What, in fact, could have been at the heart of the matter, causing the discrepancy?


A. The software she uses conflicts with other applications she is using;

B. Nothing, since this could never have happened;

C. Cpk does not directly use the individual data in question, but instead uses summary statistics from the data;

D. Subgroup size was undoubtedly too large.


Copyright 2001 PQ Systems.

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