basic of software estimation-cost and effort estimation
- 1. Basics Of Software Estimation- Efforts And Cost Estimation Techniques
- 2. 1.What is software estimation ? Software estimation is the process of estimating the time, effort, and resources required to complete a software project or specific tasks within it. It is a crucial step in project planning, as accurate estimation helps avoid schedule and budget misalignments that can lead to project failure.
- 3. Basics of software estimation The need for historical data: • Most estimating methods need information about past projects. • However, care is needed when applying past performance to new projects because of possible differences in factors such as programming languages and the experience of staff. • If past project data is lacking, externally maintained datasets of project performance data can be accessed. • One well-known international database is that maintained by the International Software Benchmarking Standards Group (ISBSG), which currently contains data from 4800 projects.
- 4. Measure of work: • Direct calculation of costs or time is difficult at the early planning stage. • The time to complete software will depend on the individual capability and experience of staff not yet identified. • Implementation time and costs will also depend on the particular technologies selected. • The usual practice is therefore to start by expressing work size independently of effort using a measure such as source lines of code (SLOC), sometimes expressed as KLOC thousands of lines of code). • The estimation of SLOC is of course itself problematic and may not be relevant when parameter- driven application-builders are used. • Alternative size measures have been proposed, such as function points which are explained in more detail later in this chapter, it can also be argued that SLOC counts do not take account of the complexity of the code to be produced.
- 5. Efforts and cost estimation techniques 1.Bottom-up estimating. 2.Top down estimating.
- 6. 1.Bottom-up estimating: • With the bottom-up approach the estimator breaks the project into its component tasks. • With a large project, the process of breaking it down into tasks is iterative: each task is decomposed into its component subtasks and these in turn could be further analysed. • It is suggested that this is repeated until you get tasks an individual could do in a week or two. • The bottom-up part comes in adding up the calculated effort for each activity to get an overall estimate. • The bottom-up approach is best at the later, more detailed, stages of project planning. If this method is used earlier, assumptions about the characteristics of the final system and project work methods will have to be made. • Where a project is completely novel or there is no historical data available, the estimator would be forced to use the bottom-up approach.
- 7. 2.Top down estimating: • Top-down estimating is a method of evaluating a project or budget as a whole and then separating it into smaller components. • With a top-down approach, professionals create an overall plan or budget for a project without defining the particulars. • These professionals would then give the project budget or plan to others who can better evaluate the specific costs or plan details. • This technique relies on the opinions of experienced managers and data from similar past projects. • As a result, it shouldn’t be expected to generate a highly accurate estimate that will align with actual costs during project development.