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Donald J. Wheeler

Quality Insider

Three Questions for Success

The necessity of using operational definitions

Published: Tuesday, March 1, 2011 - 05:30

All improvement efforts require a framework. No matter what we are doing, we all need some way to align our efforts and focus on a specific objective. During my 40 years in this business, I have seen many different models offered as frameworks for improvement. Most of these have been variations on two basic forms. First, back in the 1980s, there were various versions of plan, do, study, act (PDSA). More recently, we have had define, measure, analyze, improve, control (DMAIC) models. This column will reveal the three fundamental questions that form the basis for all of these models. Answer these three questions, and you will have a road map for success. The many different improvement models simply dress up these three questions with different details.


The ideal

The first question is: What do you want to accomplish? Until you have a clearly stated objective, you risk everyone running off in different direc­tions, working on their own pet projects, and not coop­erating for the common good. Whether it is a specific project with a limited scope, or the general day-to-day operations of your or­ganization, a clearly stated purpose or objective is important to help focus the thoughts and efforts of everyone involved. Any situation in which this question remains unanswered will rapidly deteriorate into chaos. However, merely specifying your ob­jective will not be enough.

The methodology

The second question is: By what method will you accomplish your objective? While it may be necessary to have a goal, merely having a goal is, by itself, not sufficient. Remember the old saying, “If wishes were horses, then beggars would ride.” Until you have a plan for achieving your objective, it will be nothing more than a dream. Moreover, your plan will need to identify the discrepancies between the goal and the current state of affairs, and it will also need a methodology for moving toward the goal.

The judgment

The third question is: How will you know when you have accomplished your objective? If you are going to have a goal, and if you hope to move toward that goal, then you will also need some way to measure how far you have come and how far you have yet to go. Of course, the greatest obstacle to knowing when you have accomplished your objective is the fact that data always vary. Any measure you might use will go up or down from month to month. If you do not know how to separate routine variation from a signal that a change has occurred, you will not know if you have made any progress toward your goal.

Historical context for the three questions

Walter Shewhart discussed these three questions in the context of making a product. He referred to them under the headings (1) specifica­tions, (2) production, and (3) inspection. W. Edwards Deming talked about these three questions in terms of (1) having a criterion, (2) having a test method for determining compliance to the criterion, and (3) having a decision rule for interpreting the re­sults of the test. Regardless of the nomenclature, these three questions define the essence of how to get things done. Until we can answer the second and third questions, all of our targets, all of our goals, and all of our plans are merely wishes and hopes. To turn dreams into reality, we must have some specific method for making them come true, and some way to judge when they have come true.

In his second book, Statistical Method from the Viewpoint of Quality Control (The Graduate School, U.S. Dept. of Agriculture, 1939), Shewhart returned to the idea embodied in these three questions and showed how a process behavior chart (1) defines an ideal, (2) provides a methodology, and (3) allows us to make a judgment.

Figure 1: What do you want to accomplish?

Specifically, in figure 1 the natural process limits on an X chart define the process potential. They define what a predictable process has produced and what it is likely to continue to produce. When a process is operated unpredictably, these limits approximate what that process can be made to produce. To use Shewhart’s word, the natural process limits approximate the ideal of what the process can do when it is operated up to its full potential. They define what any process can accomplish.

In figure 2 the running record of the individual values defines the actual pro­cess performance. Whenever a point goes outside the bounds of the natural process limits, it identifies a departure from the routine, a change in the process, and the presence of an assignable cause of exceptional variation. By identifying these points, the process behavior chart provides us with a methodology for when to look for assignable causes. When we can iden­tify an assignable cause and move it from the set of uncontrolled factors to the set of controlled factors, we will be removing a significant source of varia­tion from the product stream. By removing sources of variation from the product stream, we are not merely maintaining the status quo, but are rather tightening up on the process variation and improving both the predictability of the process and the consistency of the process out­comes. So the process behavior chart gives us a methodology for actu­ally moving our process to­ward the ideal.

Figure 2: By what method will you accomplish it?

Finally, in figure 3, by combining both the process potential and the process per­formance on the same graph, the process behavior chart allows us to judge how close our process is coming to operating up to its full poten­tial. The absence of points outside the limits tells of a reason­able degree of predictability. For an unpredictable pro­cess, the number of points outside the limits and the extent to which they fall outside the limits will quantify the degree of unpredictability.

Figure 3: How will you know when you have accomplished it?


The general framework defined by these three questions has been called an operational definition. Operational definitions allow you to get down to business. When you have the answers to the three questions you have what you need to succeed. Leave one of the three questions unanswered, and all you will have is the basis for an argument.

As may be seen above, the pro­cess behavior chart provides us with an operational definition of how to get the most out of any process. When you use a process behavior chart in this way, it becomes the locomotive for your improvement efforts. You do not have to work on improving the measurement process first. You do not have to first do a failure modes and effects analysis (FMEA) to think of everything that might go wrong. You do not have to brainstorm to find a problem to work on. You simply listen to your production process and let it tell you what to fix and when to fix it. When you successfully fix a problem, the chart will show this success. When you fail to fix a problem, the chart will continue to nag you.

For more on how this works, see my columns on “Two Routes to Process Improvement” from May 5 and 6, 2010.

This article is an excerpt from the author’s book, Twenty Things You Need to Know (SPC Press, 2008).


About The Author

Donald J. Wheeler’s picture

Donald J. Wheeler

Dr. Wheeler is a fellow of both the American Statistical Association and the American Society for Quality who has taught more than 1,000 seminars in 17 countries on six continents. He welcomes your questions; you can contact him at djwheeler@spcpress.com.



A workable operational definition

Somewhere between 1993 and 1996, I remember being taught about operational definitions during my Quality Engineer degree classes from the University of Miami by Dr. Howard Gitlow. He worked with Dr. Deming for a while. He said that, according to Deming, an operational definition had three parts. An operational definition consists of:

1) A criterion to be applied to an object or to a group;

2) A test of the object or group; and

3) A decision method as to whether the object or group did or did not meet the criterion.

Above all, the operational definition was such that all concerned parties could agree on it. Gitlow used the Deming example of 50% wool and 50% rayon. I have never been able to find this kind of definition in the TQM or SPC books, anywhere. I used to look at new quality books to see if they defined it this way. Your article is the first that I have seen the three parts of the definition in print. No matter what, in practice, this definition seems to work quite well for me. Thank you Dr. Gitlow.

Thank you, Dr. Wheeler, for your columns.

Claire Jones

Huntsville, AL

Sci Method and Op Definition

Howdy.  You cannot find this in Quality books.  The original came from Operational Philosophy, stemming from Hayakawa, A J Ayer, K Popper, and others long before 1969.  It is the basis for Sci Method, where the roots date back to Aristotle (Phil of Science) for the first form (Essentially, structured repeated sensations (experiments) leads to experiences and knowledge).  A good book is "Operational Philosophy", A. Rapoport, International Soc. for General Semanitcs, 1969 under "Is X True?" where the "operational definition" format is described as a formal approach to an operational definition of "truth", as opposed to the other definitions of 'truth' that were defined at the time.  The format is given by:


--> Each assertion implies predictions to be tested by conceivable operations (Ideal and Methodology -- or perhaps "Goal/Objective, Decision criteria, Plan")

--> The tests are carried out (methodology/Execute the plan)

--> The predictions are verified. (Judgment, 'conclusions, results including paths to new 'truths')


This leads to 5 results:  If all 3 steps are performed: The assertion is "true/false or true to a probability".  If we conceive of the tests, but never act, (step one only) then the assertion is "indeterminate" [Eg. "Pluto is made of cheese" I can conceive of tests -- space ship, etc. -- but I haven't made the trip yet].  If there are no conceivable or realistic tests, then the assertion is "meaningless" [Eg. "Love is green ether"].   You should be able to see the root of the scientific method here. 

There are many renditions of the scientific method, and you can see that this is one view and it contains all the items we normally consider as part of the sci method.  "Quality" did  not invent the Operational Definition -- the roots are in the phil. of science -- hence, why you cannot find the references in quality books.  It has been around for centuries in a variety of similar approaches. 

Three Questions for Success

Hello Mr. Wheeler:

Thank you again for sharing your wisdom. Your three questions remind me of what I learned from Deming's body of knowledge. What is the organization's aim? By what method with the aim be attained? How will you know?

Thank you!




Dirk van Putten