kontrollikaavio

Kontrollikaavio, also known as a control chart, is a statistical tool used to monitor and control a process. It was developed by Walter A. Shewhart in the 1920s as part of the statistical process control (SPC) methodology. The primary purpose of a kontrollikaavio is to determine whether a process is in a state of statistical control, meaning that the process is predictable and stable over time.

A kontrollikaavio typically consists of a central line representing the average of the process, and upper and lower control limits that represent the natural variability of the process. These limits are usually set at three standard deviations from the central line. Data points are plotted on the chart, and if they fall within the control limits, the process is considered to be in control. If data points fall outside the control limits, it may indicate that the process is out of control and requires investigation.

There are several types of kontrollikaavios, including the X-bar and R chart, the X-bar and S chart, and the C chart. Each type is used for different types of data, such as continuous data or attribute data. Kontrollikaavios are widely used in various industries, including manufacturing, healthcare, and service sectors, to ensure product quality, process stability, and continuous improvement.