For instance, [2] reported on the assessment of mental fatigue in inspection task in electronic component assembly factory. The researcher found that resting time and shift work affected mental fatigue of workers. In addition, [3] conducted a study in a relay manufacturing factory. It was found that workers had pains and fatigue, which ultimately affected their safety and work performance. Symptoms of fatigue included weakness, lack of energy, tiredness, exhaustion, palpitations (feeling the heart beating), dizziness, shortness of breath, etc [4]. It was found that the type of task, shift work, and the amount of products, were factors that highly affected the worker fatigue. Reference [5] applied Fuzzy set theory to study the impact of task and shift work on mental fatigue of workers in coating department, stove department, and quality control department in sanitary ware factory. It was found that the type of work (department), as well as shift work highly affected the worker mental fatigue. Similarly, [6] applied Fuzzy set theory to study mental fatigue occurred in cutting-pipe and shaping-pipe workers by measuring f