Previously, I discussed my concerns about organizations not properly managing corrective actions or process variation. While corrective actions were covered before, this piece focuses on variation.

“Variation” has several meanings, such as a slight change in condition or a distinct form of something. In ISO 9001, it refers to process deviations, which are either:

1. Random Variation – unpredictable factors inherent to the process, controllable via statistical methods (SPC).
2. Systematic Variation – predictable, identifiable sources like equipment errors, often correctable to improve quality.

Controlling variation is vital for product consistency, and ISO 9001 encourages standardization and continuous improvement. Notably, Dr. Shewhart and Dr. Deming emphasized the risks of ignoring variation.

Product variation can be positive—providing options in size, color, or material as a marketing strategy. For example, a T-shirt may come in various sizes and colors, offering multiple choices.

However, negative product variation means inconsistency: ordering three “extra large” shirts (blue, green, and red) might yield different fits due to mislabeling or poor process control, causing customer dissatisfaction.

Effective process control, including graphical monitoring techniques, is essential to ensure product quality and operational efficiency by minimizing undesirable variation.

This graphical representation demonstrates a process functioning within six standard deviations, aligned with customer specifications. Ideally, this scenario would assure the producer of consistent process performance. However, if the process is not properly controlled, alternative patterns may be evident in the graphical output, and its appearance over time can differ significantly from the example shown above.

Variation can help offer different products, but if not controlled during production or providing service, it can harm customer satisfaction and increase costs.