The lower bound (LB) and upper bound (ULB) are the two parameters required by the Uniform (or rectangular) distribution. This distribution is the simplest of all distributions. It can be interpreted as meaning that the random variable can exist only in a linear range of α to β (lower bound to upper bound) and that the probability of occurrence is directly proportional to the interval length. To specify a fixed amount of time, you can make the upper and lower bounds equal.