Estimates

5. January 2011 π mal Daumen = ?

What is the accuracy of the estimate?

For cost estimates, always specify two numbers: minimum and maximum. As project planning progresses, the uncertainties become ever smaller. For example according to PMI:

Project Progress	Boundary Values
ROM – Rough Order of Magnitude Estimate	-50% … +100%
Preliminary Estimate	-25% … +50%
Budget Estimate	-10% … +25%
Definitive Estimate	-5% … +10%
Final Estimate	0%

Results from previous projects are an important input. The maturity of the organization influences the accuracy of the estimates.

Three-point estimation from PERT

Estimate = (Optimistic + 4 * Realistic + Pessimistic) / 6
Standard Deviation = (Pessimistic - Optimistic) / 6
Uncertainty = root of the sum of the squares of all standard deviations

Function Points

standardized, enable company-wide comparison
Function Point User Group IFPUG
parametric methods, eg COCOM
Function point methods, eg COSMIC ISO 19761
own example: zitat-service_CFP.pdf und zitat-service_CFP.ods

Agile Projekte

story points, relative to each other
estimated exams
planning poker

Additional

Delphi method systematic, multi-level expert survey estimation method
Social and Technical Reasons for Software Project Failures, Capers Jones
Software Cost Estimating Methods for Large Projects, Capers Jones
Pi mal Daumen, Barbara Lange, iX 1 / 2010, S. 124 ff. (in German)