Deming introduced very practical ideas of process control as a means to limit variations in product quality. Today, it is called defined process control. Deming came at quality from the point of view of the product: make the product the same way each time and make it work within limits that are acceptable to the customer. The modern poster child for defined process control is Six Sigma. An explanation of Six Sigma is given in the Appendix at the end of this chapter.
Deming was influenced by the work of the process statistician Walter A. Shewhart, who is credited with identifying the fact that processes have two variables: assignable cause and chance cause.
Assignable cause is systemic and capable of being corrected and main- tained to an economical minimum. Assignable cause is what agile teams address in the retrospective review after each review and each release.
Chance cause is randomly occurring in frequency and intensity, not al- ways present in the process, and is mitigated by establishing performance limits for a given process. Agile handles chance cause two ways:
1. Only scheduling backlog for an iteration that is about 80% of the predictable throughput, thereby leaving “white space” for absorbing chance cause
2. Scheduling empty iterations as buffers to catch the overflow of debt that accumulates due to chance cause
A project management tip
W. Edwards Deming’s impact on agile projects
Deming focused on eliminating unsatisfactory results before they reached the customer. In agile parlance, every object must pass its unit, functional, and system test.
The modern version of Deming and Shewhart is Six Sigma. Suffice it to say, however, that defined process control is not what agile is about. Agile stresses empirical process control, meaning that circumstances in the mo- ment are drivers for process design and control limits. That said, there are elements of Six Sigma that are adaptable to agile methods.
A project management tip
Six Sigma is supportive of agile
• Six Sigma provides a very effective problem solving method
(define, measure, analyze, improve, control [DMAIC]), which enhances the plan-do-check-act (PDCA) cycle.
• The principles of DMAIC are usable without invoking other
aspects of Six Sigma.
• Six Sigma brings understanding of the defect opportu-
nity space, and promotes the idea of setting limits at the boundaries of customer satisfaction.
• Many defects will never be known and others are not eco-
nomical to fix. All have the potential to contribute to the customer experience.
Joseph Juran Favors the Customer
More in line with agile thinking, Juran began the shift of the quality ef- fort—away from Deming’s product focus and toward a customer focus. He is known for his advocacy of the Juran trilogy: quality improvement, planning, and control.
Juran stressed the quality concept of fitness to use. He believed that meet- ing a specification is a necessary condition, but insufficient without fitness to use—that is, honoring the customer’s idea of product value and utility. In other words, features are not valuable unless they are everyday useful.
Juran’s ideas are what agile practitioners think of as favoring customer value over following a plan.
Juran defined five parameters that make up fitness to use:
1. Quality of design, a judgmental parameter with grades of goodness 2. Conformance to standards and customary expectations of the
market
3. Availability, a consequence of frequency of breakdown and rapidity of repair
4. Safety in use
5. Usability in a customer’s setting
Among tools, Juran popularized the Pareto chart, which he named after Italian economist Vilfredo Pareto who recognized the phenomenon of the 80-20 rule in his study of business activity.
The Pareto chart is a histogram arranged in descending order that shows distinct problems according to how frequently each occurs. One distinct problem might be a paper jam, and it might occur 100 times a quarter. The paper jam might be the most frequently occurring problem observed.
The 80-20 rule states that most histograms show that 80 percent of all problem occurrences are linked to only 20 percent of distinctly identified problems.
So, if by example, 1000 occurrences are reported, and there are 80 dis- tinct problems among the 1000, by the 80-20 rule, 800 of every 1000 oc- currences are forecast to be attributable to 16 of 80 distinct problems.
A project management tip
Joseph Juran’s impact on agile methods
• Juran shifted quality toward a concern for the customer
and away from the goodness of the product.
• The agile interpretation of Juran is to value customer satis-
faction over following a plan.
• The concept of fitness for use, a synonym for customer
satisfaction, was promoted by Juran as a quality manage- ment concept.
• The Pareto chart helps to focus agile teams on the most
important features and functions.
Philip Crosby: Zero Defects and Free Quality
Philip Crosby came along a generation after Deming and Juran. Working in the aerospace and defense industry, Crosby became fixed on pushing Dem- ing’s ideas of assignable cause to the point of zero defects. He also authored the principle of doing it right the first time, known as DRIFT.
Crosby is best remembered for inventing the idea that quality is free! In his formulation, the cost of conformance is just the cost of doing business the right way. Thereby, the cost of quality is free; only the cost of noncon- formance is an add-on.
A project management tip
Crosby invents the idea that quality is free!
• Agile teams understand and practice the DRIFT principle.
• Although zero defects is laudable, agile methods look to
the customer to put a priority on fixing defects. Some de- fects are not economically repairable and will not be fixed.
Module 2—Discussion for Critical Thinking
In this module, three different ideas of quality are presented: business effi- ciency, product excellence, and fitness for use. This is similar to other busi- ness models that have a similar triangle. In the spirit of triangulation, which leg of the triangle would you make longer (dominant), and which gets the short end?