Focused Operations Management

Chapter 14. The Effects of Fluctuations, Variability, and Uncertainty on the System

Fluctuations

Uncertainty related to faults and disruptions is referred to as fluctuations. This word serves as a general term for all of the seemingly unexpected situations—problems, malfunctions, interruptions, and disturbances.

Murphy's Law says that if something can go wrong, it will, and it will cause maximum damage at the most inconvenient time. Occasionally, this law is referred to as the bread and butter law. If a buttered slice of bread can drop to the floor, it will; if it drops, it will fall butter‐side down, damaging the new carpet. Some people would add that if the slice fell butter‐side up, we had spread the butter on the wrong side. The O'Toole principle adds that “Murphy was an optimist.”

Sources of Fluctuations

Fluctuations can be classified by their source:

Demand fluctuations

• Variability in demand

• Seasonality

• Technological changes and changes in preferences

For example, fluctuations in the development department of a high‐tech company might involve:

• Technological uncertainty (knowledge gap)

• Changes in customers' requirements

• Unavailability of critical purchased items

• Delays of subcontractors

• Uncertainty of market demand

Evolution of Fluctuations in a Process

Consider the planning of a new line of services, products, or development as depicted in Figure 14-1 . Every task that enters the system (a patient receiving treatment, a request to develop a smart piece of software, or assembly in production) ...