3punktsmetoder

3punktsmetoder, or three-point estimation methods, are a family of estimation techniques that use three possible outcomes to determine a central value or a range for a quantity such as duration, cost, or risk. They are commonly used to incorporate uncertainty into planning and decision making.

One widely used variant is the PERT method (Program Evaluation and Review Technique). It uses optimistic (O), most likely (M), and pessimistic (P) estimates and calculates the expected value as E = (O + 4M + P)/6. A related measure is the standard deviation, approximated by SD = (P − O)/6, reflecting uncertainty in the estimate. A simpler variant is the triangular distribution, where only three points (min, mode, max) are provided, and the expected value is typically (O + M + P)/3 or computed from the distribution.

Applications include project management, cost estimation, risk assessment, and forecasting in fields such as software development and construction. The approach helps teams communicate uncertainty and build buffers into schedules and budgets.

Strengths include the ability to incorporate uncertainty and to produce a single reference value and a quantified range. Limitations include reliance on subjective judgments, potential bias, and the assumption that the three estimates capture the relevant uncertainty. It is important to obtain independent estimates and to update values as more information becomes available.

See also: PERT, three-point estimation, risk analysis, project management.