Table 4.

The order relationship and relative importance of indicators at different levels.

Indicator level	Order of importance	Order relationship	Relative importance($r_k$)
Human factors	X3 > X1 > X4 > X2	$X_1^{\ast }{>X}_2^{\ast }>X_3^{\ast }>X_4^{\ast }$	1.2, 1.4, 1.2
Equipment factors	X6 > X8 > X7 > X9 > X5	$X_5^{\ast }{>X}_6^{\ast }>X_7^{\ast }>X_8^{\ast }>X_9^{\ast }$	1, 1.2, 1.2, 1.4
Environmental factors	X11 > X10 > X13 > X12	$X_{10}^{\ast }{>X}_{11}^{\ast }>X_{12}^{\ast }>X_{13}^{\ast }$	1.2, 1.4, 1.8
Management factors	X16 > X14 > X15 > X17 > X18 > X19	$X_{14}^{\ast }{>X}_{15}^{\ast }>X_{16}^{\ast }>X_{17}^{\ast }>X_{18}^{\ast }>X_{19}^{\ast }$	1.2, 1, 1, 1.2, 1.4