Browse Teach Curate

Reference Class Forecasting

A technique for estimating a project's duration or cost by looking at how long a class of similar past projects actually took, rather than reasoning from the specifics of the current plan. Proposed by Flyvbjerg as a direct countermeasure to the planning fallacy, since outside data is far less prone to optimistic bias than an inside, step-by-step forecast. Used to produce estimates a team can defend when a plan-based estimate turns out to be wrong.

Chief Galen Tyrol Video

Reference Class Forecasting: Estimating from Outside Data, Not Inside Reasoning

Bent Flyvbjerg — the researcher who proposed the technique as a countermeasure to the planning fallacy — explains estimating a project's cost/duration from a class of comparable past projects rather …