Six Sigma practitioners know that operational definitions are definitions to do business with. An operational definition can be defined as a clear and understandable description of what is to be observed and measured, such that different people collecting, using and interpreting data will do so consistently. An operational definition is a concept to guide what properties will be measured and how they will be measured. There is no single right way to write an operational definition, only what people agree to use for a specific purpose. The concept is simple enough, but those who work on organizational change and renewal sometimes have difficulty with operational definitions.

In Six Sigma practice, the importance of operational definitions is clear. And equally clear are the consequences that can result when a project team fails to well-define a working definition. For example, it was a shock to the U.S. space exploration program when, in 1999, the Mars Polar Orbiter was incinerated in the Martian atmosphere. Analysis of this costly failure revealed that the spacecraft burned and crashed into the planet’s surface because a group of engineers had written the orbiter’s instructions in English units and the on-board computer translated them into metric units. Oops! Consider also the 36 days of absolute electoral chaos that followed the presidential election of 2000, and the seemingly endless ballot recounts by poll officials in Florida. How consistently do you think the “pregnant chad” was interpreted? Both of these examples illustrate the types of problems that can occur when operational definitions are not precise.

Frequently, Six Sigma practitioners are faced with quality features that are described by words open to interpretation. This is especially true in the service industries. Abstract quality features such as “courtesy,” “timeliness,” “friendliness” and a favorite today, “world-class,” have to be divided into components that result in uniform interpretation. It would be impossible to negotiate a service level commitment based on the “timely” delivery of a product or service. But a service level commitment that specifies delivery within a specified period – four hours, or ten days, or two months – can be measured and tested, and the results then used for decision-making.

One challenge in developing operational definitions is to break these abstract quality features into observable (measurable) parts. For example, consider an understandable bill. Everyone would agree that a bill should be understandable, but not everyone may have a common understanding of what that means. It is so much clearer if the abstract term “understandable” is removed and replace it with specific, observable parts. There is something to work with if it is agreed that the bill must be accurate (reflective of actual charges), that different types of charges must be distinguishable, and the promotional codes must be applied correctly. It is possible to measure the components of the bill in such a way that everyone has the same interpretation of the quality of billing service provided.

Problems with operational definitions problems can exist in any organization. It is important to the validity of measurement systems and project outcomes that operational definitions are clearly defined for those individuals who are responsible for collecting and using data. All of this leads to the real point of this article – that Six Sigma practitioners can take a lesson from moms about operational definitions. Moms are pretty good at taking the abstract and breaking it into pieces that kids can understand and relate to. Let’s look at some examples.

As a kid, I was out the door on Saturdays as soon as my chores were complete. From the age of six on, I knew the essence of an operational definition, even if the term itself was not known to me. I knew that chores were not considered complete until I had taken the linens off my bed and put them in the laundry hamper, picked up toys and vacuumed my room. I also knew that there would be consequences, if I ignored the definition of “complete.” As I grew older, the operational definition of completed chores changed, but I always knew explicitly what it entailed.

Being outdoors, playing with friends and riding my bike were the greatest joys in my life. Left to my own devices, I would have stayed outside until I dropped. But when I was small, Mom had another operational definition that was to be observed at all cost – be home “by dark.” By dark, could be broadly interpreted in some households, but in my experience, the definition was very precise. In my house, that meant I had five minutes, and only five minutes, to be home and in the house once the streetlights in the neighborhood came on.

I have a sister who is three and a half years younger than I. My sister is quite the adventurer. As a child, she constantly challenged my parents by doing the unexpected – never malicious activities, just not the “normal kid stuff” they anticipated. When we went out to play together as I got a little older, my Mom charged me with keeping my free-spirited sister out of “mischief.” The meaning was clear to me, if not to my sibling – keep an eye on your little sister and make sure she stays out of trouble and comes home with you.

Once, I decided to stay and play kickball with my friends. My sister did not want to play and left to go home alone. I should have gone home too, but stayed to play, ignoring my mother’s instructions to keep my sister out of mischief. Imagine my dismay when I arrived home about an hour later and saw our lawn covered with oranges. To understand the magnitude of this problem, one needs to know that I grew up in Florida and our house was built smack dab in the middle of a prolific orange grove. There were literally thousands of oranges on the ground. My sister had challenged a number of the neighbor kids to a contest to see who could pick the most oranges. When Mom got home, I was in big trouble, because I had failed to mind the operational definition to keep my sister out of mischief. As a result, we ate oranges at every meal, squeezed orange juice for hours, and gave away tons of the fruit. What we couldn’t eat, squeeze or give away, my sister and I had to pick up and dispose of when it spoiled.

As I got older, the operational definition of things like “be good” changed, but I always knew explicitly what my Mom meant. In other words, operational definitions of expectations at my house were always clear. It’s a lesson from childhood that has served me well as an adult. When defining defects and/or measures for a Six Sigma project, I think about clarity that is needed to ensure a common understanding…and I remember Momma.

About the Author