Software Estimation Process

 A software estimation process that is integrated with the software development process can help projects establish realistic and credible plans to implement the project requirements and satisfy commitments. 

®    Establish Estimate Scope: Define and document estimate expectations. When all participants understand the scope and purpose of the estimate, misunderstandings among the project group and contradictory assumptions about what is expected to become clear.

®    Establish Ground Rules and Assumptions: If detailed functionality is not known, ground rules and assumptions should clearly state what is and isn’t included in the estimate. Issues of COTS, reuse, and other assumptions should be documented as well.

®    Collect Data: Certain core information must be obtained in order to ensure a consistent estimate. Not all data will come from one source and it will not all be available at the same time, so a comprehensive data collection form will aid your efforts.

®    Size Software: Size is generally the most significant (but certainly not the only) cost and schedule driver. The overall scope of a software project is defined by identifying not only the amount of new software that must be developed, but also must include the amount of preexisting, COTS, and other software that will be integrated into the new system. Product size is generally be expressed as source lines of code (SLOC) or function points,

®    Prepare Baseline Estimates: To prepare the baseline estimate there are various approaches that can be used, including guessing (which is not recommended), using existing productivity data exclusively (also not recommended), the bottom-up approach, expert judgment, and cost models.

®    Quantify Risks & Risk Analysis: Risk is characterized by a loss of time, or quality, money, control, understanding, and so on. The loss associated with risk is called the risk impact. For each risk, we must determine what we can do to minimize or avoid the impact of the event. Risk control involves a set of actions taken to reduce or eliminate risk.

®    Review, verify, and Validate Estimate: There are many ways to validate an estimate. Both the process used to build the estimate and the estimate itself must be evaluated. Ideally, the validation should be performed by someone who was not involved in generating the estimate itself, who can view it objectively. When reviewing an estimate you must assess the assumptions made during the estimation process. Make sure that the adopted ground rules are consistently applied throughout the estimate. 

Document Estimate and Lesson and Learned: Each time you complete an estimate, you should document the pertinent information that constitutes the estimate and record the lessons you learned. By doing so, you will have evidence that your process was valid and that you generated the estimate in good faith.