火灾消防安全评价2.pdf

384 EVALUATION OF FIRE SAFETY
Because of the exponent property, this method requires that all ratings be greater than one.
When an attribute has fractional ratings, they should be consistently multiplied by some power
of ten to meet this requirement.
The weighted product method may produce more variability in results. Since the attribute
ratings are multiplied, a small measurement error in one attribute can generate a significant
variation in the score. This makes the method less appropriate when attribute ratings are the
result of subjective determinations with potentially large variances.
Weighted product is the scoring model used in the Gretener method described earlier in
this chapter.
Analytic hierarchy process (AHP)
The Analytic Hierarchy Process discussed in the previous section on attribute rating is also widely
used as a multiattribute evaluation scoring method. It has also been adapted to the Edinburgh
point system model for a study of fire safety in dwellings (Shields and Silcock, 1986). However,
there are limitations to this use of AHP in a fire safety evaluation point system.
The Analytic Hierarchy Process is not as intuitive or transparent as the arithmetic combining of
attribute weights and ratings. Also, as has been previously discussed, AHP significantly restricts
the number of attributes that can be considered. Judgment of pairwise comparisons quickly
becomes cognitively onerous as the number of attributes increases. Seven attributes produce 21
pairwise comparisons, which is approaching the maximum reasonable effort for this process. Even
AHP computer software limits the number of attributes to nine. Finally, although this is seldom
the case in fire safety evaluation, if the practical range of the attribute ratings is not known, AHP
can be subject to distortion and rank-reversal.
Although AHP has the advantage of measurable consistency in pairwise comparisons, it d