How to choose the right method to estimate how much or when the size of the software work? Common software cost estimation methods are there?
Software Effort Estimation methods are: analogy, analogy, equation method. In general workload estimating software size estimation should result as input, then take the equation method to estimate. But when some special cases, such as the demand is very vague, but can not estimate the time scale, can be directly used to estimate direct analogy and analogy workload.
Analogy belongs to "estimate" based approach. The project will be evaluated in the past one or more items to compare projections to determine the similarities and differences of particular places, and finally this difference to be adjusted based on the actual workload.
Note that when using the analogy, the selected item to be assessed history items must be highly similar, the historical data to select a data within the organization, and be sure to adjust the difference therebetween. Although the analogy is by far the most reliable theoretical estimation method, because it is based on "estimates," which, inseparable from the subjective assessment of personnel, it is also often estimates have a significant bias.
Analogy belongs to "count" based approach. When the project to be assessed and completed projects similar in some project properties (such as applications, system size, complexity, the development team experience, etc.), can be carried out using the software cost estimation analogy. It is based on extensive historical data to determine the sample project predicted value of the target item.
Note that when using the analogy, when an insufficient number of samples for the selection can be screened by comparing the individual item attribute selection, comprehensive adjustment work according to the result.
When the workload estimate using equation method, regression analysis should be considered based on the actual situation of development organizations, establish regression equation. Can all affect factors are taken into account to establish multiple-equation, or you can calculate the preliminary results based on some of the impact factor, and then adjust the results.