This post describes what is software project estimation and what are the metrics of software estimation & different estimation methods.
What is Software Project Estimation?
A successful project is one that is deliverable on time, within the budget and with the required quality. Here are some specific targets are set that the project manager along with his team tries to meet. In this process making realistic estimates is very crucial. A project manager has to estimate the effort which affects the cost and of duration which affects the delivery time.
Difficulties in Software Project Estimation
Some of the difficulties of estimation arise from the invisibility and complexity of the software. Some of the other difficulties include the following:
- Subjective Nature of Estimation:-People tend to underestimate the difficulty of small tasks and overestimate that of large ones.
- Political Implications:- Different groups within an organization have different objectives, For example the development managers may want to press the estimators to reduce the cost estimates to encourage higher management to approve more and more projects. Whereas some ofter group might try to increase the estimates to create a comfort zone for themselves ( Considering any future risks or budget slippage).
- Changing Technology:- With rapidly changing technologies it is difficult to use the experience of previous projects on new ones.
- Lack of homogeneity of project experience
Metrics for Project Size Estimation
Accurate estimation of problem size is very important to the satisfactory estimation of time, effort and cost. In order to, accurately estimate project size we need to define some appropriate metrics or units which are as follows:
Line of Code (LOC)
LOC is the simplest of all matrics available here the size is estimated by counting the number of sources instructions in the developed program. LOC which gives the numerical value of the problem can vary widely with individual coding style.
Function Point Metric (FPM)
FPM was proposed by Albrecht, one of the important advantages of using FPM is that it can be easily used to estimate the size of a software product directly from problem specification. This is different to the LOC metric where size can be accurately determined only after the product has been fully quoted. The conceptual idea underlying FPM is that the size of a software product directly depends on the number of functions or features supported by it. A software product with many features will naturally have a larger size than a product supporting less number of features.
Project Estimation Methods
Estimation of various project parameters is a basic planning activity, important parameters that are estimated are project size, effort, duration of cost. These estimates not only help customers but also are useful in resource planning and scheduling.
Emperial Techniques:
This technique is based on making an executed guess of project parameters. Here experience in the development of a similar product is helpful. These techniques include:
- Expert Judgement Technique
- Delphi Cost Method
- Estimation By analogy