Perusvaihtelu

Perusvaihtelu, also known as basic variability or basic fluctuation, is a Finnish term used in the context of quality control and statistical process control (SPC). It refers to the inherent variability that exists in any process or system due to common causes. These common causes are always present in the process and are often related to the system itself, such as variations in materials, equipment, or environmental conditions.

In the context of SPC, perusvaihtelu is an essential concept as it helps to distinguish between common cause variation and special cause variation. Common cause variation is predictable and stable, while special cause variation is unpredictable and often indicates a problem or change in the process. By understanding and monitoring perusvaihtelu, organizations can better control their processes, improve quality, and reduce waste.

The term perusvaihtelu is often used in conjunction with control charts, which are graphical tools used in SPC to monitor process performance. Control charts have upper and lower control limits that are set based on the perusvaihtelu of the process. If a data point falls outside of these limits, it may indicate the presence of special cause variation.

In summary, perusvaihtelu is a fundamental concept in quality control and statistical process control. It represents the inherent variability in any process and is used to distinguish between common and special cause variation. By understanding and managing perusvaihtelu, organizations can improve process control and quality.