## Defuzzification

Finally, a crisp value for OSUS (step 9 in Fig. 1) is computed via the height method of defuzzification,

$$\text{OSUS}=\frac{{\displaystyle \sum _{\begin{array}{l}\text{allfuzzysets}L\\ \text{ofOSUS}\end{array}}{y}_{L}{\mu}_{L}\text{(OSUS)}}}{{\displaystyle \sum _{\begin{array}{l}\text{allfuzzysets}L\\ \text{ofOSUS}\end{array}}{\mu}_{L}\text{(OSUS)}}}$$where *y _{L}* is the

*peak value*of the fuzzy set

*L*—a value of OSUS for which the membership function of

*L*is maximized.

For the example given in the previous section, only I, FH, and H are involved
in the defuzzification. It is seen in Fig.
6c that *y*_{I} = 0.5, *y*_{FH} = 0.625,
and *y*_{H} = 0.75. Therefore, the overall sustainability is
given by