Most Popular Methods Of Software Estimation.

• Parametric Estimating

An estimating technique that uses a statistical relationship between historical data and other variables (for example, square footage in construction, lines of code in software development) to calculate an estimate for activity parameters, such as scope, cost, budget, and duration. This technique can produce higher levels of accuracy depending upon the sophistication and the underlying data built into the model. An example for the cost parameter is multiplying the planned quantity of work to be performed by the historical cost per unit to obtain the estimated cost.

• Cocomo (Constructive Cost Model)

The most fundamental calculation in the COCOMO model is the use of the Effort Equation to estimate the number of Person-Months required to develop a project. Most of the other COCOMO results, including the estimates for Requirements and Maintenance, are derived from this quantity.

The COCOMO calculations are based on your estimates of a project's size in Source Lines of Code (SLOC). SLOC is defined such that:

• Only Source lines that are DELIVERED as part of the product are included -- test drivers and other support software is excluded
• SOURCE lines are created by the project staff -- code created by applications generators is excluded
• One SLOC is one logical line of code
• Declarations are counted as SLOC
• Comments are not counted as SLOC

• SLIM ( Software Life Cycle Management )

SLIM enables a software cost estimator to perform the following functions :

• Calibration Fine tuning the model to represent the local software development environment by interpreting a historical database of past projects.
• Build an information model of the software system, collecting software characteristics, personal attributes, computer attributes etc.
• Software sizing SLIM uses an automated version of the lines of code (LOC) costing technique.
• SLIM is not widespreadly used.

• Function Point Analysis

Function Point Analysis (FPA) is an ISO recognized method to measure the functional size of an information system. The functional size reflects the amount of functionality that is relevant to and recognized by the user in the business. It is independent of the technology used to implement the system.

The unit of measurement is "function points". So, FPA expresses the functional size of an information system in a number of function points (for example: the size of a system is 314 FP).

The functional size may be used:

To budget application development or enhancement costs

To budget the annual maintenance costs of the application portfolio

To determine project productivity after completion of the project

To determine the Software Size for cost estimating

• Pert Evaluation and Review Technique (PERT)

PERT is a method to analyze the tasks involved in completing a given project, especially the time needed to complete each task, and identifying the minimum time needed to complete the total project.

The most recognizable feature of PERT is the "PERT Networks", a chart of interconnecting timelines. PERT is intended for very large-scale, one-time, complex, non-routine projects.

• Analysis Effort Method

The analysis effort method is a method for estimating the duration of software engineering projects. It is best suited to producing initial estimates for the length of a job based on a known time duration for preparing a specification. Inputs to the method a numeric factors which indicate Size (S), Familiarity (F) and Complexity (C). These, with a duration for preparing the software specification can be used in a look up table (which contains factors based on previous experience) to determine with length of each of the following phases of the work. These being Design, Coding and Unit testing and Testing. The method does not include any times for training or project management.

This method should be used as one of a number of estimation techniques to obtain a more accurate estimate.