This chapter describes the four main methods of estimating and their approximate levels of accuracy. These methods are: subjective (+/– 20%–40%), parametric (+/– 10%–20%), comparative (+/– 10%), and analytical (+/– 5%). The need to always allow a contingency is stressed and a diagram shows how the accuracy percentage improves as the project moves from the concept phase to the production phase.
Estimating; subjective estimating; parametric estimating; comparative estimating; analytical estimating; contingency allowance
Estimating is an essential part of project management, since it becomes the baseline for subsequent cost control. If the ...