Environmental Engineering Reference
In-Depth Information
Table 3 Random index
n
1
2
3
4
5
6
7
8
9
10
RI
0.00
0.00
0.58
0.90
1.12
1.24
1.32
1.41
1.45
1.49
Table 4 Evaluation factors weights using AHP
Evaluation
factor
Frequency in
references ( F 1 )
Adaptation with
kind of product ( F 2 )
Easily
understand ( F 3 )
Easily
measurement ( F 4 )
0.09
0.48
0.16
0.27
weight
CI = MAX
n
n 1
(3)
CR = CI
RI
(4)
The number 0.1 is the accepted upper limit for CR. If the final consistency ratio
exceeds this value, the evaluation procedure has to be repeated to improve consistency
(here CR = 0.004). Table 4 represents a set of grades of evaluation factors importance
obtained AHP.
Results showed that adaptation with kind of product is the most important
factor for considering criteria in supplier selection process which often overlook.
4.3 Part C
Candidate criteria are ranked by TOPSIS technique using a nine point likert scale
with 1 as lowest and 9 as highest. TOPSIS is a multiple criteria decision making
method which is initially proposed by Hwang and Yoon ( 1981 ). The technique
is based on the idea that the optimal solution should have the shortest distance
from the positive ideal solution and the farthest from the negative ideal solution
(Oztaysi 2014 ). A solution is determined as a positive ideal solution if it maxi-
mizes the benefit criteria or minimizes the cost criteria. On the other hand, the
solution which maximizes the cost criteria or minimizes the benefit criteria is
called the negative ideal solution (Wang and Elhag 2006 ).
Candidate criteria are scored based on four evaluation factors by purchase
manager of company (Table 5 ) and composed decision matrix.
In the initial step of the technique, decision matrix ( i = alternatives , j = evaluation
factors ) are constructed. After composing decision matrix, normalized decision
 
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