How Can the Check Standard Influence Measurement Process Capability

Purpose: The main objective of the paper is an analysis of the behaviour of capability indices under different conditions. It is assumed that the metrological properties of a check standard are correct, however, the uncertainty of the check standard affects the evaluation of the measurement process capability. The paper analyses individual cases of the influence of the check standard bias and its influence on the measurement process capability. Methodology/Approach: Statistical analysis of both the measurement process and the check standard is provided at the beginning. Development and analysis of possible cases, when the bias of a check standard affects the calculated capability index of a measurement process follows. Findings: The paper confirmed the theoretical assumption that a bias of a check standard can affect the calculated capability index of a measurement process, thus shifting the judgment on the measurement process capability. Research Limitation/Implication: The paper is based on the theoretical assumptions of the measurement process capability as well as on the analysis of the possible behaviour of a respective check standard. Originality/Value of paper: The paper clarifies that several particular and specifically selected cases of bias of a check standard may affect the resulting capability index negatively/positively, which may lead to inaccurate decisions on measurement process capability. This is confirmed by simulations of a biased check standard, clearly visualizing the shifts in capability indices.