What is a quality control chart?
The quality control chart (QC chart) is used in quality management for the evaluation of inspection data. It is used to evaluate processes with regard to their quality constancy over time (process stability). If a significant change in the process takes place, the quality control chart signals the direction of the change. This can be an increase in quality dispersion and/or change in the position of the quality characteristic. Statistical sample characteristic values (e.g. sample mean value and sample standard deviation of the quality characteristic) and warning, intervention and tolerance limits are displayed graphically for this purpose.