Basic equation of parametric estimation
Science has proven: There is no linear correlation between size & effort and effort & time!
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.