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each community is awarded a 'score' for each of the criteria included in the ranking process. For each criterion, a high score indicates that the provision of sewerage to that community is important while a low score indicates that it is less critical;
not all the criteria included are of equal importance. It is necessary to weight the scores so that important criteria have a larger impact on the final result than minor ones;
a weighted score is produced by multiplying the score by the weight;
the total score for a community is the sum of the weighted scores given for each criterion; and
communities having the highest scores are most favoured for the immediate implementation of a sewerage scheme.
The magnitude of the scores is unimportant: only the ranking of the communities matters. An example of the selection process is shown in Table 3.1. The table concentrates on technical and
Table 3.1 Example of a matrix for prioritising the provision of sewerage
Town
Projected
population
On-site sanitation
failure
Polluting
industries
Unit cost of
construction
Sc
Wt
T
Sc
Wt
T
Sc
Wt
T
Sc
Wt
T
A
10
1
10
1
3
3
1
1
1
4
2
8
B
9
1
9
7
3
21
10
1
10
7
2
14
C
6
1
6
1
3
3
10
1
10
5
2
10
D
3
1
3
1
3
3
1
1
1
2
2
4
E
2
1
2
1
3
3
1
1
1
3
2
6
F
2
1
2
1
3
3
10
1
10
5
2
10
G
2
1
2
1
3
3
5
1
5
2
2
4
H
2
1
2
1
3
3
5
1
5
1
2
2
J
1
1
1
4
3
12
10
1
10
10
2
20
K
1
1
1
1
3
3
1
1
1
2
2
4
L
1
1
1
7
3
21
10
1
10
6
2
12
Sc = score (the impact of a criterion on a town).
Wt = weight (the importance of a criterion in the selection process).
T = total (the multiple of the score and the weight).

(table continued on next page)

 
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