June  2003  

Vol. 5, No. 6

Quality Quiz
Black belt not attainable without knowledge

Dr. Noah Tahl has learned about the use of control charts, standard deviations, and histograms—all in a 2-hour workshop that he attended during a national health care conference. He has seen for himself how these concepts help hospitals and other health care institutions to organize and analyze their data, and is determined to use statistical process control to improve measures of quality at St. Maybe Hospital. In this effort, he engages his staff in a training effort to assure that all members of his department will be on the same page when it comes to statistics.

And speaking of pages, he keeps at least a page ahead of the group that he is training in these methods. So while everyone else may be on the same page, Dr. Noah Tahl stays up late at night to assure himself that he knows more than those whom he is training. It’s a never-ending struggle to stay ahead.

After he has demonstrated the formula for calculating standard deviation, and shown his trainees how control charts and histograms will help them understand processes, he introduces CHARTrunner a software program that creates charts from data in established spreadsheets such as Excel. “This will make your life easier,” he promises, but as it turns out, it may be on the verge of making his own life harder.

Alec Smart, one of his department managers, comes across the concept of the coefficient of variation as he explores the printout of his charted data. “What does it mean when the coefficient of variation is 11.92?” he asks.

Although the chapter on coefficient of variation is not one that Dr. Tahl has studied yet, he feels compelled to respond, especially since the entire class is looking expectantly at him and waiting for his answer. “That’s really the sum of the log of the standard deviation,” he mumbles. Although no one understands what he means, trainees nod their heads and take notes.

Was this the right definition for coefficient of variation? If so, was Dr. Noah Tahl’s response an inspired guess or an intuitive speculation? Is it important in health care? Stay tuned for more about this exciting turn of events in the dynamic life of Dr. Noah Tahl, statistician.
Is he correct?

Select from the following the best description of the coefficient of variation:

A) the capability of a process;

B) whether a process is in or out of control;

C) the peakedness of a distribution;

D) the ratio of a standard deviation to the mean in a data set.

Copyright 2003 PQ Systems.

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