## 2 Process Capability  
The characteristics of the course of the process are best determined using appropriate statistical methods (PN-EN ISO 9004:2018-06) [28]. This involves the need to obtain quantitative results of measuring process variables (PN-EN ISO 9001:2015-10) [29] that will allow effective process monitoring. The basic goals of process analysis are as follows [30]:  
1. Formulating directions and priorities for improving their course. 2. Measurement of process improvement effects. 3. Regulation of the process flow. An ideal, stationary process should be characterized by the lack of dispersion of results--any selected process variable characterizing its output during the process has a constant value. In reality (practice) there are no stationary processes. The result of each real process is in the form of a distribution of the values of the selected process variable--it is characterized by dispersion. Thus, the basic parameters for assessing the quality of processes are:  
* A measure of the distribution dispersion of a selected process variable (process dispersion). * Measure of the location of the distribution of the selected process variable (process centering). The assessment of the quality of production processes is associated with the assumption that each product delivered to the customer is endowed with a defect (loss); the smaller it is, the higher is the quality of the product [31; 32]. This loss is the higher the more the value of the product feature considered deviates from the target value, including within the tolerance range. This contradicts the view expressed by [PERSON] that the product quality is constant if the property under consideration falls within the tolerance range (Figure 1). The tolerance field is defined here by the lower LSL and upper USL tolerance limits. Therefore, given the approach presented by [PERSON], every product whose parameters deviate from the target value is characterized by a loss of quality [33; 34]. To characterize the process with the capability specified for the selected process variable x, the width of the range in which we accept the obtained process results should be compared with the adopted limit of the process variable distribution, e.g., with the range of \(6\sigma\)[35]. Indicators for process capability are increasingly used in industrial practice. Due to the introduction of a process approach in quality management in 2000 [29], it became necessary to monitor processes. \"The organization should define the processes needed in the quality management system and their application in the organization and should (...) define and apply the criteria and methods (including monitoring, measurement and related performance indicators) needed to ensure the effective conduct and supervision of these processes\". The point 8.5.1. of this standard refers to \"the ability to achieve the planned results of production processes and services provided.\" In industrial practice, the planned result is the required width of the tested property range of the manufactured product. The process capability is a special inherent feature of the process resulting from the statistical description of one of the outputs (adopted for the description of the process) carried out in a selected period of time. The process capability is the relationship between the required tolerance of the considered product property--process output--treated as a process variable and the obtained dispersion of the value of this variable--the result of the adopted method of limiting the distribution of variable values obtained in a given process duration. Graphic interpretation of the process capability assessment is presented in Figure 2.  
The simplest form of the process capability indicator, denoted by \(C_{P}\), is defined as follows:  
\[C_{P}=\frac{\text{required tolerance}}{\text{process dispersion}}, \tag{1}\]  
This coefficient is used when the instantaneous average process value \(\overline{x}\), obtained on the basis of measurements, is equal to the assumed--purposeful process value \(T\).