Kyvykkyysindeksi

Kyvykkyysindeksi, or the *capability index*, is a statistical measure used primarily in quality management and process control to assess the performance of a manufacturing or production process. It quantifies how well a process is capable of meeting specified tolerances for a product or service. The index is widely applied in industries such as automotive, aerospace, and electronics, where precision and consistency are critical.

The capability index is derived from process variation data and compares it to the allowable tolerance range. The most common indices are **Cpk** and **Cp**, where **Cp** evaluates the potential capability of a stable process, while **Cpk** considers both process stability and centering. A higher index value indicates better process capability, with values above 1.33 typically considered acceptable for most applications, though industry standards may vary.

The calculation of the capability index involves several key parameters: the process mean (μ), process standard deviation (σ), and the upper (USL) and lower (LSL) specification limits. For **Cp**, the formula is (USL - LSL) / (6σ), while **Cpk** adjusts for process centering by taking the minimum of two values: (USL - μ) / (3σ) and (μ - LSL) / (3σ). These metrics help identify whether a process consistently produces output within desired limits.

Beyond manufacturing, the concept of capability indices has been adapted in other fields, such as healthcare and software development, to evaluate system performance against defined benchmarks. Improving a process’s capability index often involves reducing variation, adjusting process settings, or refining control measures. Regular monitoring and recalculation of the index ensure ongoing compliance with quality standards.