Another sensitivity analysis method has been referred to as importance measures in the literature [9]. Quantitative measures of sensitivity were defined to measure the
importance. The Fourier amplitude sensitivity test (FAST), the Sobol’I’s method [10] , the measures of importance of Iman and Hora [9], and those of Ref. [11] all coincide with
importance measures. Generally, the system output is generated by numerical method which is time-consuming when complex problems have to be solved. Meanwhile, Monte Carlo method is employed to obtain statistics of system output. In order to achieve more insight in the
model behavior in an efficient way, Sobol’I’s method is a choice