Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 2 1 2016 06 06 25 31 EN Maryam Zamani Department of Biostatistics, School of Health, Kerman University of Medical Sciences, Kerman, Iran. Abbas Bahrampour Department of Biostatistics and Epidemiology, School of Health Kerman, Research Center for Modeling in Health Kerman University of Medical Sciences, Iran. Nouzar Nakhaee Department of Neurology, Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran. 2016 06 06 2016 06 06 Background & Aim: Chronic diseases impact not only on patients but also on their family members’ lives. This study aims to determine dimensions of Family Dermatology Life Quality Index (FDLQI) questionnaire by the use of classic and Bayesian factor analysis (BFA) factor. Methods & Materials: In this study, FDLQI questionnaire distributed among 100 family members of dermatological patients. BFA is exploited to determining dimension and contribution of items of the questionnaire in different sample size. BFA is examined using the Monte Carlo-Markov chain algorithm. All the above analysis is done in sample size 100, 130, 150. Results: In this study, 100 family members of dermatological patient attended to evaluate Persian version of FDLQI questionnaire. A mean age of participants was 37.1 years (± 12.3). A mean score of FDLQI was 15.4 (± 5.5) with maximum and minimum scores of 30 and 6, respectively.Exploratory FA revealed a one-factor solution that accounted for 45.87% of the total variance. The unidimensional model was concordance by confirmatory FA. For more exploration, BFA was performed. Two factors extracted when iteration is done. Conclusion: It appears that when sample size diminished, Cronbach’s alpha and Kaiser–Meyer–Olkin increased. Among 10 items of the questionnaire, item 9 mostly appears differently in results. https://jbe.tums.ac.ir/index.php/jbe/article/view/47 https://jbe.tums.ac.ir/index.php/jbe/article/download/47/37