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Format: VoseGTU(min, leftmode, rightmode,max,m,n, U)
Generalized Trapezoid Uniform (GTU) equations
The Trapezoid Uniform distribution is a generalization of the Triangle distribution, well-suited for subjective estimation. It's PDF has a flat part in the middle rather than a peak at the mode. It consists of three stages, and its PDF plot looks like a trapezoid.
It takes four parameters: min, left mode, right mode and max. For the limiting case min=left mode and max=right mode this becomes a uniform distribution, and for left mode=right mode this becomes a triangle distribution.
The generalized trapezoidal distribution allows the slopes to be curved, governed by two extra parameters m and n: m for the curvature on the left and n on the right. The values m=1 and n=1 correspond to straight slopes.
The GTU distribution may be used to model processes that are characterized by a growth, steady and decline stage.
The GTU distribution can also provide a flexible alternative to the PERT and triangle for subjective estimation.
Van dorp (2003) provides a thorough explanation of the derivation and use of the GTU.
VoseGTU generates values from this distribution or calculates a percentile.
VoseGTUObject constructs a distribution object for this distribution.
VoseGTUProb returns the probability density or cumulative distribution function for this distribution.
VoseGTUProb10 returns the log10 of the probability density or cumulative distribution function.