The four basic steps in Software Project Estimation are − Estimate the size of the development product. Estimate the effort in person-months or person-hours. Estimate the schedule in calendar months. Estimate the project cost in agreed currency. Observations on Estimation. Estimation need not be a one-time task in a project. It can take place. Estimates are typically a necessary evil in software development. Unfortunately, people tend to assume that writing new software is like building a house or fixing a car, and that as such the contractor or mechanic involved should be perfectly capable of providing a reliable estimate for the work to be done in advance of the. Effort Estimation for Software Development - Software effort estimation has been an important issue for almost everyone in software industry at some point. Below I will try to give some basic details on methods, best practices, common mistakes and available tools. The estimate process used here will help you manage projects better, and you will get better at estimation through personal experience. It is important to remember that estimates can vary and change throughout the course of a project. This is why it is necessary to use separate templates for managing software development estimation projects. Before starting any software development project, we need to assess the project in terms of effort/time and cost. A good project estimation will lead to a successful project while a wrong estimation may end up in project failure. In order to successful software project & proper execution of task, the Estimation Techniques plays vital role in software development life cycle. The technique which is used to calculate the time required to accomplish a particular task is called Estimation Techniques. To estimate a task different.
For any new software project, it is necessary to know how much it will cost to develop and how much development time will it take. These estimates are needed before development is initiated, but how is this done? Several estimation procedures have been developed and are having the following attributes in common.
Uses of Cost Estimation
Cost Estimation Models
A model may be static or dynamic. In a static model, a single variable is taken as a key element for calculating cost and time. In a dynamic model, all variable are interdependent, and there is no basic variable.
Static, Single Variable Models: When a model makes use of single variables to calculate desired values such as cost, time, efforts, etc. is said to be a single variable model. The most common equation is:
C=aLb
Where C = Costs
L= size a and b are constants
The Software Engineering Laboratory established a model called SEL model, for estimating its software production. This model is an example of the static, single variable model.
E=1.4L0.93
DOC=30.4L0.90 D=4.6L0.26
Where E= Efforts (Person Per Month)
DOC=Documentation (Number of Pages) D = Duration (D, in months) L = Number of Lines per code
Static, Multivariable Models: These models are based on method (1), they depend on several variables describing various aspects of the software development environment. In some model, several variables are needed to describe the software development process, and selected equation combined these variables to give the estimate of time & cost. These models are called multivariable models.
WALSTON and FELIX develop the models at IBM provide the following equation gives a relationship between lines of source code and effort:
E=5.2L0.91
Software EngineeringIn the same manner duration of development is given by
D=4.1L0.36
The productivity index uses 29 variables which are found to be highly correlated productivity as follows:
Software Development Time Estimation
Where Wi is the weight factor for the ithvariable and Xi={-1,0,+1} the estimator gives Xione of the values -1, 0 or +1 depending on the variable decreases, has no effect or increases the productivity.
Example: Compare the Walston-Felix Model with the SEL model on a software development expected to involve 8 person-years of effort.
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Solution:
The amount of manpower involved = 8PY=96persons-months
(a)Number of lines of source code can be obtained by reversing equation to give:
Then
L (SEL) = (96/1.4)1⁄0.93=94264 LOC
L (SEL) = (96/5.2)1⁄0.91=24632 LOC Software Development Estimation Models
(b)Duration in months can be calculated by means of equation
Software Development Estimation Sample
D (SEL) = 4.6 (L) 0.26
= 4.6 (94.264)0.26 = 15 months D (W-F) = 4.1 L0.36 = 4.1 (24.632)0.36 = 13 months
(c) Productivity is the lines of code produced per persons/month (year)
Software Development Estimation Framework
(d)Average manning is the average number of persons required per month in the project
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