en Application of Fuzzy System in Psychological Tests: Optimize the Number of Questions for WHOQOL-BREF عمومى General پژوهشي Research The WHOQOL-BREF is one of the best known questionnaires for measuring the quality of life. It is currently available in more than 40 languages and has been used frequently in cross-cultural comparison studies on subjective well-being and quality of life studies. Some research shows that due to certaincultural biases Iranian respondentshave no tendency or willingness to responding some questions, more specially, question 21, in WHOQOL-BREF. The main aim of the current research was to use the ability and flexibility of fuzzy systems to analyse the WHOQOL-BREF questions to reduce some unclear or doubtful questions. A fuzzy system model proposes to diminish the errors that produce ambiguous concepts by not responding to certain biased questions.TheWHOQOL-BREEquestionnaire was analyzed and both the traditional model and the fuzzy model analyses were compared for results using fuzzy systems.As a result, question 21 was removed from the WHOQOL-BREF questionnaire used by the fuzzy system. 51 75 http://ijpb.ir/browse.php?a_code=A-10-39-107&slc_lang=en&sid=1 ghanbari ghanbari ghanbari hamid reza Yes department of psychology university of sistan and baluchestan department of psychology university of sistan and baluchestan mehrdad mazaheri mehrdad mazaheri No department of psychology ferdowsi university of mashhad amp__AWT_NOKT_COMMA__ university of sistan and baluchestan department of psychology ferdowsi university of mashhad amp__AWT_NOKT_COMMA__ university of sistan and baluchestan hasan mishmast nehi mishmast nehi No department of mathematics university of sistan and baluchestan department of mathematics university of sistan and baluchestan