In the fuzzy DEA model whose inputs and outputs are fuzzy and efficiency score is precise, all DMUs could not be ranked when the number of efficient units is no less than two.

• 摘要在输入、输出数据为模糊数而效率值为准确值的模糊DEA模型中，会出现有两个以上有效单元，从而无法对所有决策单元进行全排序的情形。