✐ “M20N16” — 2009/2/17 — 1:01 — page 71 — #1 ✐ ✐ ✐ ✐ ✐ Available online at jims.ms.tku.edu.tw/list.asp International Journal of Information and Management Sciences 20 (2009), 71-88 An Additive Scale Model for the Analytic Hierarchy Process Yuh-Yuan Guh Rung-Wei Po Department of Business Administration Institute of Technology Management Chung Yuan Christian University National Tsing Hua University R.O.C. R.O.C. Kuo-Ren Lou Department of Management Sciences & Decision Making Tamkang University R.O.C. Abstract This study presents an additive scale model for the Analytic Hierarchy Process (AHP) that suits the decision problem using a linear preference comparison. This study discusses issues related to mathematical denotation, axiom, transitivity and numerical analysis for the additive scale model of AHP. The least squares method and correlation analysis are used to obtain the relative criteria weights and consistency index. Moreover, a fuzzy model is devel- oped to enhance the practical flexibility of the additive scale model of AHP in applications. Two examples are used to demonstrate that the criteria weights derived from the proposed approach are steady and effectively reflect the intensity of perception, and the consistency index is invariant to the scale multiplier employed. Keywords: Multicriteria, Analytic Hierarchy Process, Pairwise Comparison Scale, Ratio Scale, Additive Scale, Scale Transitivity. 1. Introduction The Analytic Hierarchy Process (AHP) is one of the most used multicriteria decision- making approaches. Proposed by Saaty in the mid 1970s, the AHP combines tangible and intangible features to derive priorities associated with problem alternatives. The AHP uses the well-defined mathematical structure of a reciprocal matrix and the eigenvalue approach to generate true or approximate weights. The AHP is a structural framework Received Feburary 2007; Revised May 2007 and October 2007; Accepted December 2007.