other Mathematical Modeling and Applications of OR Mathematical Modeling and Applications of OR پژوهشی Original <span class="fontstyle0">Cost efficiency models evaluate the ability of decision-making units (DMUs) to produce current<br> outputs at minimal cost. In real applications, the observed values of the input-output data and<br> their corresponding input prices are imprecise and vague. This paper employs a fuzzy data<br> envelopment analysis (Fuzzy DEA) method to study cost efficiency of DMUs. In previous studies<br> on the cost efficiency, no attention has been paid to the issue of ranking problem in fuzzy<br> environment. In addition, adequate accuracy is ignored in regards to appropriate range of fuzzy<br> cost efficiency scores. In this study, the proposed method is applied to assess fuzzy cost efficiency<br> in accordance with the </span><span class="fontstyle2"> </span><span class="fontstyle0">-level based approach. In this method, data information is considered<br> as triangular fuzzy numbers. The main idea is to convert the fuzzy DEA model into a family of<br> parametric crisp models to estimate the lower and upper bounds of the </span><span class="fontstyle2">a</span><span class="fontstyle0">-cut of the membership<br> functions of the cost efficiency measures. Moreover, the problem of ranking DMUs is investigated<br> based on the fuzzy cost efficiency, using a new method. Finally, the proposed method is illustrated<br> applying a numerical example, and then comparisons between the proposed method and previous<br> approaches are carried out.</span><br style=" font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " > &nbsp; Cost Efficiency, Data Envelopment Analysis (DEA), Fuzzy Sets, The a-level Based Approach 25 42 http://iors.ir/journal/browse.php?a_code=A-10-1422-18&slc_lang=other&sid=1 jafar pourmahmoud jafar pourmahmoud pourmahmoud@azaruniv.ac.ir 1111111111 1111111111 Yes Azarbaijan Shahid Madani University Azarbaijan Shahid Madani University Naser Bafek Sharak Naser Bafekr Sharak naser.bafekr@azaruniv.ac.ir 1111111111 1111111111 No Azarbaijan Shahid Madani University Azarbaijan Shahid Madani University