Interval Type 2- Fuzzy Rule based System Approach for Selection
of Alternatives using TOPSIS
Abdul Malek Yaakob
1,2
, Ku M. Naim Ku Khalif
2
,
Alexander Gegov
2
and Siti Fatimah Abdul Rahman
3
1
School of Quantitative Science, Universiti Utara Malaysia, 06010 Sintok, Kedah, Malaysia
2
School of Computing, Buckingham Building, University of Portsmouth, Portsmouth, PO1 3HE, U.K.
3
Department of Mathematics & Statistics, Universiti Teknologi MARA(Perlis), 02600 Arau, Perlis, Malaysia
Keywords: Fuzzy Decision Making, Ranking Alternative, TOPSIS, Type 2 Fuzzy Set, Fuzzy Rule based System,
Influence Degree, Stock Selection, and Assessing Ranking Performance.
Abstract: The paper considers fuzzy rule based system for multi criteria group decision making problem. A novel
version of TOPSIS method using interval type 2 fuzzy rule based system approach is proposed with the
objective of improving the type 2 TOPSIS ability to deal with ambiguity through the combination of the
mathematical process involved in the type 2 TOPSIS with the expert empirical knowledge. On the other
hand, a hybrid analysis of decision making process that requires the use of human sensitivity to reflect
influence degree of decision maker can be expressed by a fuzzy rule base. To ensure practicality and
effectiveness of proposed method, stock selection problem is studied. The ranking based on proposed
method is validated comparatively using Kendall’s Tau rank correlation. Based on the result, the proposed
method outperforms the established non-rule based version of type 2 TOPSIS in term of ranking
performance.
1 INTRODUCTION
Multi criteria decision making has received great
attention recently in optimization problems
(Shidpour et al. 2013)(Awasthi et al. 2011) and
(Şengül et al. 2015). This is due to the fact that the
ability of decision makers in providing result that is
consistent with actual situation remains as major
concern in decision making environment.
Conventional Technique for Order of Preference by
Similarity to Ideal Solution (TOPSIS) was
originally developed in (Hwang, C.L.Yoon 1981).
Later, the conventional to T1 TOPSIS was enhanced
to provide additional flexibility in represent the
uncertainty (Chen 2000). A decade later, a fuzzy
rule based version of T1-TOPSIS was develop,
which provide a basis for automatic generation of a
rule base to assist the analysis of decision making
problem (Santos and Camargo 2010).
In 2010, a TOPSIS method based on interval
Type 2 (T2) fuzzy set was introduced which
demonstrate additional degree of freedom to
represent the uncertainty and the fuzziness of the
real world problems. In order to improve the ability
in dealing and presenting vagueness of information
in established non rule based T2 TOPSIS
method(Chen and Lee 2010), T2 - Fuzzy Rule Based
TOPSIS (T2 FRBS TOPSIS) is introduce in this
paper, which has capability in providing a useful
way to handle MCDM problems in a more flexible
and intelligent manner but also presenting expert’s
knowledge accurately and significantly.
The paper is organized as follows. Section 2
briefly reviews the concept of interval T2 fuzzy set.
The proposed method is systematically explained in
section 3. In section 4, stock selection problem is
explained using the proposed method. Next, ranking
performance is assessed and analysis of result is
discussed in section 5. Finally, the conclusion is
drawn.
2 BASIC CONCEPT
In the following, we briefly review some basic
definitions of fuzzy sets from (Chen, 2000) and
(Chen and Lee 2010). These basic definitions and
112
Yaakob, A., Khalif, K., Gegov, A. and Rahman, S..
Interval Type 2- Fuzzy Rule based System Approach for Selection of Alternatives using TOPSIS.
In Proceedings of the 7th International Joint Conference on Computational Intelligence (IJCCI 2015) - Volume 2: FCTA, pages 112-120
ISBN: 978-989-758-157-1
Copyright
c
2015 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
notations are used throughout the paper unless stated
otherwise.
Definition 1: Fuzzy set
A fuzzy set
A
~
is defined on a universe
X
may
be given as:
()
}|),{(
~
~
XxxxA
i
A
=
μ
Where
()
]1,0[:
~
Xx
i
A
μ
is the membership
function
A
~
. The membership value
()
x
i
A
~
μ
describes
the degree of belongingness of
Xx
in
A
~
.
Throughout this paper, type-1 fuzzy number, and
type-2 fuzzy number are presented in the form of
trapezoidal fuzzy number. It is easy to deal with
because it is piece wise linear. On the other hand,
the good coverage of trapezoidal fuzzy number is a
good compromise between efficiency and
effectiveness.
Definition 2: Type-2 Fuzzy Number
A trapezoidal interval type-2 fuzzy set
A
~
can be
represented by
()
() ()()
() ()()
==
L
i
L
i
L
i
L
i
L
i
L
i
U
i
U
i
U
i
U
i
U
i
U
i
L
i
U
i
AHAHaaaa
AHAHaaaa
AAA
~
,
~
;,,,
,
~
,
~
;,,,
~
,
~~
214321
214321
as shown in Figure 1, where
U
i
A
~
and
L
i
A
~
are type-1
fuzzy sets,
L
i
L
i
L
i
U
i
U
i
U
i
U
i
aaaaaaa
3214321
,,,,,,
and
L
i
a
4
are
the reference points of the interval type-2 fuzzy set
)
~
(,
~
U
iji
AHA denotes the membership value of the
element
U
ji
a
)1( +
in the upper trapezoidal membership
function
)
~
(,21,
~
L
ij
U
i
AHjA
denotes the membership
value of the lower trapezoidal membership function
,21,
~
jA
U
i
and
ni 1
],1,0[)(],1,0[)(],1,0[)(],1,0[)(
2121
L
i
L
i
U
i
U
i
AHAHAHAH
Figure 1: Type-2 Fuzzy Number (Chen and Lee 2010).
3 PROPOSED METHOD
In this section, the authors extend the T2-TOPSIS
method from (Chen and Lee 2010) using fuzzy rule
based approach for handling multi criteria decision
making problem. The main purpose of modification
is to extend the ability of fuzzy rules based approach
into established method. Thus, the implementation
by proposed method allow the empirical knowledge
of the expert, represented by fuzzy rule, also be
considered in the decision making process.
The use of the methods associated with the empirical
knowledge of experts, allows a hybrid analysis of
the decision making problems where the process of
decision making requires the use of human
sensitivity, which often can be expressed by a fuzzy
rules base. Thus, the behavior of the system may
have greater influence then the rule defined by the
decision maker. The authors adopt the methods
described in (Santos and Camargo 2010) for the
knowledge of the influence degree of each decision
maker.
In case in which one decision maker has more
knowledge of the domain, optionally the opinion of
this expert may have greater degree of importance
than the other decision makers in the analysis of the
problem. Thus, the proposed method can identify
and aggregate the different opinions of decision
makers with varying influence degrees to suggest the
final solution. Figure 2 schematically
demonstrations such a system, where C
1
, C
2
, C
3
C
m
is the input, in this case criteria and Y represents
the output/ alternative level. The rules for such a
system are normally derived from expert knowledge.
Figure 2: Fuzzy System.
Just as in established fuzzy TOPSIS method, Table 1
and Table 2 are used to represent the importance of
criteria and the rating of the alternative. In order to
deal with influence degree of decision maker in T2
fuzzy rule based approach, Table 3 introduce here,
which implement the consequent part of the rules.
The linguistic terms that represents the consequents
of rules was named “Alternative Level” and is
represented by fuzzy sets “Very bad”, “Bad”,
“Regular”, “Good” and “Excellent”.
C
1
C
2
C
3
C
m
Y
Rule Base
Interval Type 2- Fuzzy Rule based System Approach for Selection of Alternatives using TOPSIS
113
Table 1: Linguistic terms for the importance weight of
each criterion.
Linguistic Type 2 Fuzzy Number
Very Low (VL) (0.00,0.00,0.00,0.10,1,1)(0.00,0.00,0.00,0.10,1,1)
Low (L) (0.00,0.10,0.10,0.25,1,1)(0.00,0.10,0.10,0.25,1,1)
Medium Low (ML) (0.15,0.30,0.30,0.45,1,1)(0.15,0.30,0.30,0.45,1,1)
Medium (M) (0.35,0.50,0.50,0.65,1,1)(0.35,0.50,0.50,0.65,1,1)
Medium High (MH) (0.55,0.70,0.70,0.85,1,1)(0.55,0.70,0.70,0.85,1,1)
High (H) (0.80,0.90,0.90,1.00,1,1)(0.80,0.90,0.90,1.00,1,1)
Very High (VH) (0.90,1.00,1.00,1.00,1,1)(0.90,1.00,1.00,1.00,1,1)
Table 2: Linguistic terms for rating of all alternative.
Linguistic Trapezoidal Fuzzy Number
Very Poor (VP) (0,0,0, 1,1) (0,0,0, 1,1)
Poor (P) (0,1,1,3,1,1) (0,1,1,3,1,1)
Medium Poor (MP) (1,3,3,5,1,1) (1,3,3,5,1,1)
Fair (F) (3,5,5,7,1,1) (3,5,5,7,1,1)
Medium Good (MG) (5,7,7,9,1,1) (5,7,7,9,1,1)
Good (G) (7,9,9,10,1,1) (7,9,9,10,1,1)
Very Good (VG) (9,10,10,10,1,1)(9,10,10,10,1,1)
Table 3: Linguistic term for alternative level.
Linguistic Trapezoidal Fuzzy Number
Very Bad(VB) (0.00,0.00,0.00,0.25,1,1)(0.00,0.00,0.00,0.25,1,1)
Bad (B) (0.00,0.25,0.25,0.50,1,1)(0.00,0.25,0.25,0.50,1,1)
Regular (R) (0.25,0.50,0.50,0.75,1,1)(0.25,0.50,0.50,0.75,1,1)
Good (G) (0.50,0.75,0.75,1,1,1) (0.50, 0.75, 0.75, 1,1,1)
Very Good (VG) (0.75,1.00,1.00,1.00,1,1) (0.75,1.00,1.00,1.00,1,1)
The following algorithm is conducted to get the
ranking of alternatives, whereby Step 1-5 are taken
from (Chen & Lee 2010), whereas Step 6 to Step 8
are introduced in this paper.
T2- FRBS TOPSIS algorithm
Instead of calculating the average decision
matrix as the previous TOPSIS methods(Mohamad
and Jamil 2012),(Kelemenis et al. 2011). Here, the
opinion of each decision maker evaluated
independently. Assume that there are
m
alternatives
m
AAA ,,,
21
and assume that there are
n
criteria
121
,,,,
+nn
CCCC
. Where
1+n
C
represent the
influence level of each decision maker. Let there are
k
decision makers
k
DMDMDM ,,,
21
then will
have
k
decision matrix.
Step 1: Construct Fuzzy Decision Matrix,
()
K
D
and Fuzzy Weight of Alternative
()
K
W as shown in
Eq. (1).
()
=
mnmm
n
n
K
xxx
xxx
xxx
D
21
22221
11211
and
[]
nK
wwwW
21
=
(1)
where
ij
x
and
i
w
are interval T2 fuzzy set based
from Table 1 and Table 2 respectively. Its represent
the rating and the important weights of the
th
K
decision maker of alternative
i
A with respect to
criterion
j
C
()
nj ,,1 =
respectively.
Step 2: Weighted fuzzy decision matrix
()
K
V
The weighted fuzzy decision matrix
()
K
V is shown
in Eq. (2).
[
]
nm
ijK
vV
×
=
for
mi ,,1 =
and
nj ,,1 =
(2)
where
()
ijijij
wxv =
is an multiplication of interval
T2 fuzzy set.
Step 3: Construct the ranking weighted decision
matrix
Calculate the ranking value
)(
iK
ARank (Lee and
Chen 2008), in order to find ranking value, the
maximum number
s
of edges in the upper
membership function
U
ij
v
and the lower membership
function
L
ij
v
of interval T2 fuzzy set
ij
v are defined,
where
ni 1
and
mj 1
. If
s
is odd number
and
3s
, then
1+= sr
. If
s
is even number
and
4s
, then
s
r
=
. The )(
i
ARank of interval T2
fuzzy set is shown in Eq. (3).
()
()
(
)
(
)
() () ()
() () ()
++++
+++
+++=
},{
2
},{
2
},{
1
},{},{
2
},{
1
},{
1
},{
2
},{
1
1
LUj
j
r
LUj
j
LUj
j
LUj
j
r
LUj
j
LUj
j
LUj
j
r
LUj
j
LUj
U
i
iii
iii
ii
i
AHAHAH
ASASAS
r
AMAMAMARank
(3)
where
(
)
j
ip
AM denotes the average of the elements
j
ip
a
and
()
j
pi
a
1+
()
()
()
2
1
j
pi
j
ip
j
ip
aa
AM
+
+
=
for
11 rp
()
2
11
2
1
2
1

+
=
+
=
=
q
qk
q
qk
j
ik
j
ik
j
iq
aaAS
for
11 rp
The
(
)
j
ir
AS
denotes the standard deviation of the
elements
j
ir
j
i
j
i
aaa ,,,
21
()

==
=
r
k
r
k
j
ik
j
ik
j
ir
a
r
a
r
AS
1
2
1
11
FCTA 2015 - 7th International Conference on Fuzzy Computation Theory and Applications
114
The
(
)
j
ip
AH denotes the membership value of the
element
()
j
pi
a
1+
,
21 rp
, },{ LUj and
r
is
even number.
Step 4: The fuzzy positive ideal solution
(
)
+
A
and
the fuzzy negative ideal solution
(
)
A
as shown in
Eq. (4).
(
)
++++
=
n
vvvA ,,,
21
and
(
)
=
n
vvvA ,,,
21
(4)
where
(
)
{
}
(){}
=
+
CxvRank
BxvRank
v
iij
nj
iij
nj
i
,min
,max
1
1
and
(
)
{
}
(){}
=
CxvRank
BxvRank
v
iij
nj
iij
nj
i
,max
,min
1
1
where
B
denotes the set of benefit attribute and
C
denotes the set of cost attribute and
ni 1
To calculate the distance
)(
i
Ad
+
between each
alternative
i
A and the fuzzy positive ideal solution
+
A is shown in Eq. (5).
()
()
=
++
=
m
i
iiji
vvRankAd
1
2
)( for
nj 1
(5)
Calculate the distance
)(
i
Ad
between each
alternative
i
A and the fuzzy negative ideal
solution
A
, as shown in Eq. (6).
()
()
=
=
m
i
iiji
vvRankAd
1
2
)(
for
nj 1
(6)
Step 5: The closeness coefficient
()
i
CC
Calculate the relative degree of closeness
()
i
CC of
i
A calculated as shown in Eq. (7)
+
+
=
ii
i
i
dd
d
CC
for
mi ,,1 =
(7)
Step 6: The influence Closeness coefficient of each
alternative
The influence degree of each decision maker has
been defined at this point, noting that experts with
more experience have a greater degree of influence
than the expert with less experience.
Let
=
=
K
i
i
i
K
1
θ
θ
σ
for
mi ,,1 =
(8)
Where
K
σ
represent normalized influence degree
for
th
K
decision maker.
i
θ
is the importance degree
between
0
( unimportant) and 10 (very importance)
of decision maker. Then
iKi
CCICC *
σ
=
(9)
And it is necessary to normalize the
i
ICC
()
i
NICC
to ensure that the
i
ICC value varies between 0 to 1.
i
i
i
i
ICC
ICC
NICC
max
=
(10)
Step 7: The matrix of antecedent
()
Λ and the matrix
of consequent
()
χ
A matrix of antecedents is defined as in Eq. (11)
=Λ
mnmm
n
n
XXX
XXX
XXX
21
22221
11211
(11)
where
ij
X
is a linguistic terms representing decision
maker opinion of each alternative with respect to the
criteria.
Once
i
NICC for each alternative defined by each
decision maker is obtained, it is used to determine
the consequents of alternative rules according to the
fuzzy set with higher membership in Table 3. Then a
matrix of consequents is define in Eq. (12)
=
m
Y
Y
Y
2
1
χ
(12)
where
j
Y
is a linguistic terms based on Table 3
representing the output of the system based on Eq.
(10) to find the value of
i
NICC .
Interval Type 2- Fuzzy Rule based System Approach for Selection of Alternatives using TOPSIS
115
Hence, matrix of antecedent and matrix of
consequent in Eq. (11) and (12) can be written as If-
then rule as follow:
If C
1
is X
11
and C
2
is X
12
and ... and C
1n
is X
1n
then A
1
is Y
1
If C
1
is X
21
and C
2
is X
22
and ... and C
2n
is X
2n
then A
1
is Y
2
If C
1
is X
m1
and C
2
is X
m2
and ... and C
mn
is X
mn
then
A
1
is Y
m
Step 8: The final score
()
Γ
for each alternative is
given as shown in Eq. (13).
Ω=
Γ
*
λ
(13)
where
λ
is a crisp value of aggregate membership
function of the output in Eq. (12) defined as shown
in Eq. (14)
K
K
i
ij
=
=
1
αλ
(14)
where
jij
Y
α
is maximum membership degree of
the output. In order to obtain a better representation
in the ranking made by T2- FRBS TOPSIS, It is
importance to have influence multiplier when the
alternatives have same ranking position. This show
exactly how each alternative is different even a
small difference. The following general formula to
calculate influence multiplier
()
Ω uses a marginal
closeness coefficient that has maximum membership
degree as shown in Eq. (15).
KNICC
K
i
i
=
=Ω
1
(15)
Therefore, from the value of
Γ
, the ranking order of
all alternatives can be determined. The best
alternative has higher value of
Γ
.
4 IMPLEMENTATION OF
METHOD
In this case study a Stock selection problem is
considered in which the evaluation was done by
three decision makers. These financial experts
included finance lecturer (DM1), fund manager
(DM2) and PhD finance student (DM3). They
evaluated 25 stocks (S1-S25) listed on Main Board
in Kuala Lumpur Stock Exchange (KLSE) and then
make investment recommendations according to
financial ratio considered.
The most importance ratio considered in
investment is Market Value of Firm (C1) defined as
Market value of firm-to-earnings before
amortization, interest and taxes ratio. This ratio is
one of the most frequently used financial indicators
and the lower this ratio is better. Return on Equity
(C2) used to examine how much the company earns
on the investment of its shareholders. Portfolio
managers examine ROE very carefully and used it
when deciding whether to buy or sell. The higher the
ratio is better. ROE is usually measured as net
income divide by stockholder. Dept/equity ratio
(C3), this ratio belongs to long term solvency ratios
that are intended to address the firm’s long run
ability to meet its obligations. So, it is assume by
DMs that the lower the ratio the better. Current ratio
(C4) is one of the ways to measure liquidity of
company. It explains the ability of a business to
meet its current obligations when fall due. Higher
the ratio is better. Market value/net sales(C5) is
market value ratios of particular interest to the
investor are earnings per common share, the price-
to-earnings ratio, market value-to book value ratio,
earning-to-price ratio. The lower the ratio is the
better. Price/earnings ratio (C6) measure the ratio of
market price of each share of common stock to the
earnings per share, the lower this ratio is better.
In the case study, the alternative of decision
makers to be rank and to be weighted according to
the above mention ratios are 25 stocks listed in
KLSE .In this study, Microsoft Excel was used to
calculate all the calculation involved in the
evaluating the ranking of stocks and the weight of
each criterion. The DMs use the linguistic weighting
terms in Table 1 to assess the importance of the
criteria, and make use information in Table 2 to give
rating for each alternative. All linguistic terms can
be expressed as type 2 trapezoidal fuzzy numbers as
shown in Table 1, 2 and 3. The T2- FRBS TOPSIS
algorithm introduced in Section 3 is now illustrated
for the case study of stock selection problem.
Step 1: Based on information given by experts
and applying Eq. (1), the decision matrix for each
alternative can be constructed.
The important of criteria and the rating of each are
obtained from questionnaire.
Step 2: Construct a Weighted Decision
Matrix
()
K
V
Based on Eq. (2), the normalized weighted decision
matrices can be determined, shown as follows:
()()
0.1,0.1,0.1,0.1,0.1,9.00.1,0.1,0.1,0.1,0.1,9.0
1
=w
()()
0.1,0.1,10,10,10,90.1,0.1,10,10,10,9
11
=x
FCTA 2015 - 7th International Conference on Fuzzy Computation Theory and Applications
116
Then
()()()()()
0.1,0.1,100.1,100.1,100.1,99.0
11
××××=v
()()()()()
0.1,0.1,100.1,100.1,100.1,99.0 ××××
()()
0.1,0.1,10,10,10,1.80.1,0.1,10,10,10,1.8
11
=v
Using formula stated to construct the normalized
fuzzy decision matrix.
The
10max
1
=
j
i
C
,
()()
0.1,0.1,0.1,0.1,0.1,81.00.1,0.1,0.1,0.1,0.1,81.0
0.1,0.1,
10
10
,
10
10
,
10
10
,
10
1.8
0.1,0.1,
10
10
,
10
10
,
10
10
,
10
1.8
11
11
=
=
v
v
The normalization method is to preserve the
property that the ranges of normalized trapezoidal
fuzzy number belong to
[]
1,0
.
Step 3: Construct the ranking weighted decision
matrix
Based on Eq.(3) the ranking values
)(
iK
ARank of
the trapezoidal type 2 fuzzy number
ij
v can be
calculated, illustrate for S1 as follows
()
(
)
(
)
(
)
(
)
(
)
()
() () () () ()
() () ()
() () () ()
LULU
LUL
ULULU
L
ULULU
vHvHvHvH
vSvSvS
vSvSvSvSvS
vM
vMvMvMvMvMvRank
112112111111
114114113
113112112111111
3
3221111
4
1
11
1111111111
++++
+++
++++
+
++++=
()
()
1111
0823.000095.00823.000095.0
4
1
0.10.10.10.1905.0905.0
11
++++
+++++++
+++++=vRank
Rank values for S1 are
{}
4877.5,8219.6,6119.8,9931.7,7214.9
with respect to 6 criteria respectively.
Similarly, the rank value for each alternative can be
obtained.
Step 4: The fuzzy positive-ideal solution
(
)
*
A
and fuzzy negative-ideal solution
(
)
A
Based on Eq. (4), fuzzy positive ideal solution and
fuzzy negative ideal solution are determined as
follows:
{}
3229.6,5526.9,5375.7,5526.9,7525.8,7214.9=
+
A
{}
4233.1,5259.3,1593.2,1805.1,8955.2,0533.0=
A
Using Eq.(5) to calculate the distance
)(
i
Ad
+
between each alternative and the ideal solution
+
A
=
+
)(
1
Ad
()()
2
22
3229.64877.57214.914.72.9 ++=
8858.1=
The distance between fuzzy negative ideal solution
and S1 calculated based on Eq.(6) as follows:
=
)(
1
Ad
()()
22
4233.14877.50533.014.72.9 ++=
4534.15=
Step 5: Using Eq.(7), the relative degree of
closeness
()
i
CC
of each alternative
i
A
with respect
to the fuzzy positive ideal solution
+
A
.The
calculation for
1
CC
shown as follows:
+
=
ii
i
dd
d
CC
*
1
4534.158858.1
4534.15
+
=
8912.0=
Follow the same procedure to calculate
i
CC
for
each alternative.
In the next step shows how the new criteria
1+n
C
involved in the evaluation of T2- FRBS
TOPSIS.
Step 6: The influence closeness coefficient
()
i
ICC
of each alternative
Firstly the influence degree
()
K
σ
of each decision
maker must be determined using Eq.(8) based on
their experience on the field. In this case study,
7
C
in Table 4 represent the importance degree of
decision maker. DMs evaluate themselves by giving
value 0 to 10, for uninfluential and very influential
respectively. For instance influence degree of DM
1
is calculated as follows:
7108
8
1
++
=
σ
32.0=
Following by Eq. (9) to get the influenced closeness
coefficient for
1
A
8912.032.0
1
×=ICC
2852.0=
Next, the influenced closeness coefficients need to
be normalized prior to matching the coefficient to
the linguistic terms in Table 3. As an example in this
case study, assuming the maximum value of
2852.0=
i
ICC
out of 25 stocks then the normalized
influenced closeness degree calculated as follows:
2852.0
2852.0
1
=NICC
1=
()
7214.9
11
=vRank
Interval Type 2- Fuzzy Rule based System Approach for Selection of Alternatives using TOPSIS
117
Step 7: The matrix of antecedent
()
Λ
and the
matrix of consequent
()
χ
Each decision maker has t matrix of antecedent and
consequent separately.
If
mnmm
n
n
m
XXX
XXX
XXX
R
R
R
21
22221
11211
2
1
then
m
Y
Y
Y
2
1
The rules have the following format:
If
11
X
is VG and
12
X
is VG and
13
X
is VG and
14
X
is VG and
15
X
is VG and
16
X
is VG Then
1
Y
is VG.
Now, the value of
i
NICC
can be match to the
linguistic terms for alternative in Table 3. For
instance,
1
1
=NICC
Then
1
Y
belong to interval type 2 fuzzy set VG in
Table 3.
Step 8: The final score
()
Γ for each alternative.
Based on Eq. (13) the value of final score has been
calculated. Assuming S1 has three rules R1, R2 R3
from three decision makers. For example final score
for S1 is shown below:
R1: If C1 is VG and C2 is VG and C3 is G and C4
is VG and C5 is G and C6 is G Then S1 is VG
R2: If C1 is VG and C2 is VG and C3 is F and C4 is
MG and C5 is MG and C6 is F Then S1 is VG
R3: If C1 is G and C2 is VG and C3 is VG and C4 is
VG and C5 is G and C6 is G Then S1 is VG
To calculate the value of
λ
as in Eq. (14)
Let the output of each rule for S1 are as follows
R1: VG =(0.80,0.9,0.9,1.0,1.0,1.0)
(0.80,0.9,0.9,1.0,1.0,1.0)
R2: VG = (0.80,0.9,0.9,1.0,1.0,1.0)
(0.80,0.9,0.9,1.0,1.0,1.0)
R3: VG = (0.80,0.9,0.9,1.0,1.0,1.0)
(0.80,0.9,0.9,1.0,1.0,1.0)
Then,
λ
is calculated as
3
9.09.09.0 ++
=
λ
9.0=
Furthermore, the
Ω
is calculated using Eq. (15) as
follows
From Step 6, by assuming ICC of each rule for S1
are
R1: 1.0 R2: 1.0 R3: 1.0
The value of
Ω
defined as
3
0.10.10.1 ++
=Ω
0.1=
Lastly, the final score
()
Γ
can be derived as Eq. 13
Ω=
Γ
*
λ
0.19.0 ×=
9.0=
Therefore, from the value of
Γ
, the ranking order of
all alternative can be determine. The best alternative
has higher value of
Γ
. Hence the ranking based on
proposed method (PM) can be seen in Table 4.
5 ANALYSIS OF RESULTS
For the validation purposes, the authors considered
the ranking based on established T2 TOPSIS (non-
rule based approach) and actual price change (return
on investment). The rankings are compared
descriptively using Kendall’Tau rank correlation
()
τ
(Adler 1957). The advantages of Kendall tau
correlation are its easy algebraic structure and
intuitively simple interpretation. In general, the
coefficient of tau shows the degree of concordances
between two columns of ranking data. The Tau
Coefficient can be determine by

+
=
ijij
ijij
JG
JG
τ
where
ij
G
and
ij
J
represent concordance pair and
discordances pair, respectively. In particular,
concordance pair interprets the number of observed
ranks below a particular rank which are larger than
that particular rank, whereas discordance is the
number of observed ranks below a particular rank
which are smaller than that particular rank. To test
the significant of the rank, the statistical z-score can
be define by following (Dibley & Trowbridge 1987).
)52(2
)1(3
+
=
n
nn
z
τ
Obviously, statistical z-score shows how far that
data is from the mean. The distance from the mean is
measured in term of standard deviation. The bigger
the z- score value, the more significant the ranking
to the actual ranking. Thus, based on the analysis of
Kendall’Tau Correlation in Table 5, it’s observed
that the z-score value of FRBS T2 TOPSIS is higher
than, which is outperform and more significant to
the actual ranking comparison to T2-TOPSIS.
FCTA 2015 - 7th International Conference on Fuzzy Computation Theory and Applications
118
Table 4: Ranking based investment return, established T2
TOPSIS and proposed method (T2-FRBS TOPSIS).
Stock
Ranking
Actual T2-TOPSIS T2-FRBS TOPSIS (PM)
S3 1 24 24
S1 2 1 1
S15 3 15 10
S2 4 16 13
S16 5 9 8
S23 6 3 4
S21 7 11 11
S11 8 10 7
S14 9 13 15
S25 10 6 19
S6 11 19 17
S18 12 14 12
S12 13 4 3
S24 14 22 25
S19 15 23 22
S20 16 5 5
S7 17 2 2
S17 18 17 18
S5 19 21 21
S22 20 20 20
S4 21 7 6
S10 22 12 14
S9 23 25 23
S8 24 8 9
S13 25 18 16
Table 5: Assessing the ranking performance based on
Kendal’s tau correlation.
STOCKS
T2-TOPSIS T2- FRBS TOPSIS (PM)
S3 1 23 1 23
S1 23 0 23 0
S15 9 13 14 8
S2 8 13 11 10
S16 13 7 14 6
S23 18 1 17 2
S21 11 7 12 6
S11 11 6 13 4
S14 9 7 9 7
S25 12 3 5 10
S6 5 9 6 8
S18 7 6 8 5
S12 11 1 11 1
S24 2 9 0 11
S19 1 9 1 9
S20 8 1 8 1
S7 8 0 8 0
S17 4 3 3 4
Table 5: Assessing the ranking performance based on
Kendal’s tau correlation (cont.).
STOCKS
T2-TOPSIS T2- FRBS TOPSIS (PM)
S5 1 5 1 5
S22 1 4 1 4
S4 4 0 4 0
S10 2 1 2 1
S9 0 2 0 2
S8 1 0 1 0
S13
Summation 170 130 173 127
τ
0.1333 0.1533
z 0.9342 1.0743
Kendal Tau Coefficient
0.8238
0.8577
6 CONCLUSION
In this paper, a novel variation of TOPSIS method
via extending established T2-TOPSIS method (Chen
and Lee 2010) by attached the ability of fuzzy rule
based system approach in solving the multi criteria
decision making problems. The ranking based on
proposed method is validated comparatively using
Kendall tau correlation. The results shows proposed
method (PM) outperform the established non rule
based version of type 2 TOPSIS in term of ranking
performance. The proposed method not only
provides a useful way to handle MCDM problems in
a more flexible and intelligent manner also presents
expert knowledge more accurately. In this paper,
the authors have successfully extended established
T2-TOPSIS using fuzzy system. The next objective
is to implement T2-TOPSIS using fuzzy networks,
which is new type of fuzzy system by aiming to
improve significantly the transparency of the
TOPSIS method.
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