Abstract
The fuzzy regression control chart is a functional technique to evaluate the process in which the average has a trend and the data represents a linguistic or approximate value. In this study, the theoretical structure of the “α-level fuzzy midrange for α-cut fuzzy X -regression control chart” is proposed for triangular (TFN) and trapezoidal (TrFN) membership functions. In addition, the real world application is evaluated with fuzzy X regression control charts and fuzzy R control charts for the triangular membership function.