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Sunday, August 10, 2008

Effort estimation techniques

A new project is being thought of (or even an extension of the current product). As an example, say you want to build a new shopping cart application for your website. In order to get started, besides knowing exactly what you want to build (the product details), you also need to start estimating how many people you will need and how long it will take. And this process of estimation is probably one of the more difficult parts of software development, something that can make or break a project. Suppose your estimation goes wrong, and you estimate too little effort for the project. In such a case, you will be forced to make compromises / overwork the people involved / deliver a low quality work. All of these are major factors that could cause the project to fail. Fortunately, there are a number of different effort estimation techniques that could be employed (this post just has brief descriptions, details for each of these will be covered in future posts):

# Function Point Analysis (FPA): A way to break down the work into units to express the amount of business function an information system provides to a user
# Parametric Estimating / Estimation Theory: Estimating the value based on measured / empirical data
# Wideband Delphi: A estimation theory that works on the basis of developing a consensus for the estimation (typically based on a series of group meetings)
# Cocomo: An algorithmic estimation model, using a regression formula derived from historical data and current project details
# Putnam Model: Taking data from the project (such as effort and size and fitting these data to a curve). This is an empirical model.
# SEER-SEM Parametric Estimation of Effort, Schedule, Cost, Risk.: System Evaluation and Estimation of Resources - Software Estimating Model. This model is based on a mixture of statistics and algorithms
# Proxy-based estimating (PROBE) (from the Personal Software Process): Proxy based estimating produces size estimates based on previous developments in similar application domains
# The Planning Game (from Extreme Programming): This is the process that depends on release planning and iteration planning (inside iteration planning, requirements are broken down into tasks and tasks are estimated by the programmers)
# Program Evaluation and Review Technique (PERT): PERT is intended for very large-scale, one-time, complex, non-routine projects, and has a great advantage of being able to incorporate uncertainty
# Analysis Effort method: This method is best suited to producing initial estimates for the length of a job based on a known time duration for preparing a specification
# TruePlanning Software Model: Parametric model that estimates the scope, cost, effort and schedule for software projects
# Work Breakdown Structure: In this technique, all the individual tasks are laid out with their estimates and description, and they can be summed to display the total effort

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