Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 3 1 2011 06 15 6 11 Teimour Allahyari Department of Occupational Health, Health Faculty, Urmia University of Medical Sciences, Urmia, Iran Narmin Hassanzadeh Rangi Department of Occupational Health, Health Faculty, Shahid Beheshti University of Medical Sciences, Tehran, Iran Yahya Khosravi Department of Occupational Health, Faculty of Medicine, Tarbiat Modares University, Tehran, Iran. Farid Zayeri Department of Biostatistics, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2015 10 04 Cognitive-based human errors have major contribution to performance and safety in working environment. This study designed to develop a measurement tool in order to evaluate this type of errors in the occupational settings. An Occupational Cognitive Failure Questionnaire (OCFQ) was developed. Content validity of the OCFQ was performed using a quantitative approach. Reliability of questionnaire was assessed by internal consistency and test-retest methods. A preliminary list of 35-items was prepared as a starting point. After evaluation of validity, five items were rejected. The new measurement instrument with 30-items was finally developed. The content validity index (CVI) for the final OCFQ was found acceptable (CVI=0.7).  Results show that final OCFQ was internally consistent (α=96) and intraclass correlation coefficients (ICC) was 0.99. Measurement of cognitive failure in the workplace requires a valid and reliable tool. In respect to probable outcomes of cognitive failures occurrence at work, the present study suggested that OCFQ would be a useful instrument for measurement of cognitive failure in the working environment. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/26 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/26/26