Eskandar Abdolahi - Department of Mathematics, Science and Research Branch Islamic Azad University, Tehran, Iran
Farhad Hosseinzadeh Lotfi - Department of Mathematics, Science and Research Branch Islamic Azad University, Tehran, Iran
Hilda saleh - Department of Mathematics, Science and Research Branch, Islamic Azad University, Tehran, Iran
Zohreh Moghaddas - Department of Mathematics, Science and Research Branch, Islamic Azad University, Tehran, Iran

Recently Liu et al. (2011) have provided a study on building DEA models without explicit inputs for performance evaluation of Decision Making Units (DMUs). On basis of what they provided, the DEA-WEI models, in this paper it has been verified that in the mentioned approach convexity assumption has not been properly dealt with. Thus, a modified approach has been presented and for clarity, an application of the DEA-WEI models is presented.

Data envelopment analysis, Efficiency, convexity, Data without inputs