Abstract: “Control charts are very useful tools to monitor process for evaluating variability. Although they are often used, traditional control charts have to design based on crisp values for the quality characteristics. It is also clear that the measurements of quality characteristics includes some uncertainty related with human judgments and evaluations in real case problems. When the data includes uncertainty or vagueness, the results about process variability obtained from traditional control charts are not correct. To overcome these problem, the fuzzy set theory (FST) can be successfully applied into control charts. One of fuzzy sets extensions named type 2 fuzzy sets that have fuzzy membership values can be used more effectively to design of control charts. The fuzzy control charts based on type-2 fuzzy sets are more usable in real case problems because of modelling uncertainties of human judgments and measurement systems. For this aim, one of attribute control charts named control chart f”

Keywords: Control charts, attributes, the fuzzy set theory, type-2 fuzzy sets, u control chart