CONTRIBUTION OF PRESENT RESEARCH TO UNCERTAINTY ASSESSMENT METHODS - Modelling Uncertainty in Flood Forecasting Systems - page 72

(4.43)
where the subscripts L and R represent LB (lower bound) and UB (upper bound),
respectively.
Figure 4.15. Addition of two fuzzy variables.
Similarly, the three other operations (subtraction, multiply and division) on fuzzy
variables are given by
(4.44)
(4.45)
(4.46)
In the case of random variables, suppose two random variables are related by a function
g such that
Y = g(X)
(4.47)