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    • List of Articles Ghasem Tohidi

      • Open Access Article

        1 - Generalization of the RDM model in Data Envelopment Analysis
        Hamed Taherzadeh Ghasem Tohidi Bo Hsiao
        The current study extends and provides a generalization of the range directional model (RDM). The proposed generalized RDM (GRDM) model utilizes an ideal point (IP) and anti-ideal point (AIP) simultaneously to evaluate the efficiency score. It is evident that approachin More
        The current study extends and provides a generalization of the range directional model (RDM). The proposed generalized RDM (GRDM) model utilizes an ideal point (IP) and anti-ideal point (AIP) simultaneously to evaluate the efficiency score. It is evident that approaching to the IP, not necessarily, leads to moving away from the AIP. This obviously happens when the IP, AIP, and DMU lie on a common line; however, the depicted situation usually occurs hardly ever. On the other side, there are loads of situations in which a DMU requires not only to approach the IP but also to move away from the AIP, simultaneously. The GRDM model imposes two criteria (i.e., approaching to IP and moving away from AIP) to asses DMUs. Therefore, the efficiency score, when GRDM is used, is less than or equal to the efficiency score obtained by using the RDM model; consequently, the discrimination power of the GRDM model is better than that of the RDM model due to finding more inefficiency regarding both IP and AIP. The GRDM model is unit- and translation-invariant. A numerical example is applied to demonstrate the applicability of the proposed model in comparison with the RDM model. Manuscript profile
      • Open Access Article

        2 - Profit efficiency in non competitive market
        Ghasem Tohidi Simin Tohidnia
        This paper develops a non-radial linear programming model based on the concept of directional distance function to examine the profit efficiency (inefficiency) of decision making units (DMUs) in the case where the market prices are available but can be controlled by uni More
        This paper develops a non-radial linear programming model based on the concept of directional distance function to examine the profit efficiency (inefficiency) of decision making units (DMUs) in the case where the market prices are available but can be controlled by units, and DMUs can influence simultaneously the prices and quantities of inputs and outputs to maximize the total profit. The optimal solution of the proposed model can help decision makers to evaluate and improve the profit efficiency of DMUs by changing the prices and quantities of inputs and outputs. The proposed model satisfies the important properties, units invariance and translation invariance. We present a decomposition of the profit inefficiency obtained by the optimal solution of the proposed model which can individualize quantity and price contributions to the profit inefficiency of under evaluation DMU. Finally, an empirical application to a set of 50 bank branches will be presented to illustrate the proposed approach. Manuscript profile