“…In this situation, a better way is to estimate security returns by experienced experts such as fund managers, which implies that security returns are fuzzy variables. Several researchers (Wang and Zhu, 2002;Terol et al, 2006;Fang et al, 2006;Vercher et al, 2007;, Zhang et al, 2007, Zhang et al, , 2009Huang, 2008;Li et al, 2010;Liu and Liu, 2002;Huang, 2008;Li et al, 2010; have utilized fuzzy set theory to investigate portfolio selection problem by regarding security returns as fuzzy variables instead of random variables. Different from random variables and fuzzy variables, Liu (2007) proposed the concept of uncertain variable and established uncertainty theory to study the behavior of uncertain phenomena.…”