laatuvaihtelu

Laatuvaihtelu (quality variation) is a concept used in quality management to describe the variability of quality attributes of products or services produced by a process. It encompasses variations in measurable characteristics such as dimensions, performance, durability, appearance, and conformance to specifications across units, batches, or over time. The term is used in Finnish manufacturing, quality assurance practices, and process improvement to distinguish normal, expected variation from defects.

Causes of laatuvaihtelu include both common causes inherent in a process—material properties, machine condition, environmental factors, and operator methods—and special causes such as anomalies, breakdowns, or supplier changes. Measurement error and sampling can also contribute to perceived laatuvaihtelu.

Measurement and management rely on statistical process control, control charts, and capability analysis (for example Cp and Cpk) to quantify how well a process stays within specification. Reducing laatuvaihtelu involves improving process capability, standardizing work, strengthening supplier quality, implementing preventive maintenance and calibration, and using designed experiments to identify improvement opportunities.

The concept helps set realistic tolerances, manage costs, and improve customer satisfaction by reducing waste and rework. It informs decisions about process redesign, automation, and supplier selection, and is closely related to broader quality management approaches such as Six Sigma and total quality management.

Related topics include quality control, process capability, statistical process control, and tolerance analysis.