It should be noted that the AHP requires that a problem bedecomposed into levels, each of which is comprised of elements.The elements of a given level are mutually independent, but comparableto the elements of the same level. This assumption is thefundamental to the proposed Fuzzy AHP method. Hence, the wayto categorize the risks and the relationship/nature of the risk factorsat the same level will determine the effectiveness and validityof the method. For example, in Wang et al.’s 2004 paper, therisks related to construction projects were divided into “countrylevel,” “market level” and “project level.” Under such categorization, the risk factors are strongly correlated. For instance, thecountry level risks may influence both the market and projectlevels risks, while the market level risks may influence the projectrisks. As a result, a factor at one particular level may influenceother factors at another level. For example, “the foreign exchangeand convertibility” and “inflation and interest rates” at marketlevel can cause “cost overrun” at project level. Hence, the independencyamong elements cannot be guaranteed. As a reference,when setting up the hierarchy structure for the proposed fuzzyAHP model, the categorization methods of risk factors need toensure the maximum independency among elements at the samelevel.
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