Heuristic Estimation Technique
Learning Oriented Techniques :
As techniques basically uses the concept of learning from the previous project and estimate the cost. Although intuitively very similar to expertise based techniques, heuristic estimation technique take a different angle. The objective is to find a similar system produced earlier and through knowing how the properties of the new system vary from the existing one.
Two classes of different heuristic Estimation Techniques:
- single variable model - multi variable model
- multi variable model
Single Variable Estimation Models:
It provides a means to estimate the desired characteristics Of a problem, using some previously estimated basic (independent) characteristic of the software product such as its size.A single variable estimator model takes the following form:
e= characteristic which already have been calculated.
Estimated parameter is the dependent parameter to be estimated. The dependent parameters to be estimated could be effort, duration, staff size etc.
c1 and d1 are constants- calculated from past projects.COCOMO is one of this type of models example.
Multivariable Cost Estimation Model:It has the following form
e1 and e2 are the basic independent characteristics of the software already estimated.
c1, c2, d1, d2, are constants.
Multivariable Estimation Models are expected to give more accurate estimate compared to the Single Variable Models, since a project parameters is typically influenced by several independent parameters.
The independent parameters influence the dependent parameter to different extents.
This is modeled by the constants
These constants are determined from historical data.Intermediate Model of COCOMO is an example of this