In probability theory and statistics, the trapezoidal distribution is a continuous probability distribution with lower limit a, upper limit b and modes c and d, where a < b and a ≤ c ≤ d ≤ b. Between c and d, the probability density is constant; otherwise one has the generalized trapezoidal distribution.
Special cases of the trapezoidal distribution include the uniform distribution (with a = c and d = b) and the triangular distribution (with c = d).
References
Trapezoidal distribution Wikipedia(Text) CC BY-SA