»Unique competencies in all relevant qualifications (capability, experience, complexity and other quality & cost drivers)«
The reliability of expert judgment depends very much on knowledge, capabilities, and experience and decreases with increasing project size, agility, complexity, and automation degree.
Expert judgments are person-dependent and therefore not objective, hardly reasonable, unprecise, usually not reproducible, and thus not reliable.
Studies prove, that 80 % of all expert judgments have a deviation by a factor 2 - 9 between estimates and actuals.
Basic equation of parametric estimation
Beside business or functional requirements, there are a large number of impact factors, also called quality and cost drivers, environmental factors or "soft facts". Each imapct factor has a different linear or exponential effect on effort, schedule, and costs. Science has identified up to 50 relevant impact factors (parameters) in practice.
Methods provide standardized parameters (e.g., capabilities, experience, complexity, maturity, etc.) and allow an assessment (actual or desired situation) of all impact factors on a predefined scale (default parameters). The impact of quality and cost drivers is independent of the size of a project (see Methods & Metrics).
Typical examples of these methods are e.g. COCOMO II, COQUALMO, REVIC, Karner, etc. The methods are used to convert the size of a project (see Methods) in effort and schedule. They provide all relevant parameters from the areas of organization, processes, resources, project planning, working environment, constraints, etc.