Step Review Estimate Accuracy

® Calibrate estimation techniques and models.

® As with size estimation, several models are available for estimating effort. Most of them are based on philosophies that are fundamentally mathematical, experiential, or based on regression.

Given that software estimates are imperfect, comparison of estimates with actuals provides an improved basis for management of the remainder of a given project or for future ones. Software projects are unpredictable and frequently are rescoped. The project manager re-estimates to reflect major changes. In software, unlike many other industries, the same product is never built twice. In addition to estimates taking into account the differences between a new project's specifications and previous ones, the differences in the development and delivery environment must also be considered—and with the fast-paced changes in technology, there may be no historical data upon which to base

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Some of the most widely used models for determining effort (and, therefore, cost) are the Delphi method, which is nonautomated and used for estimating effort in exactly the same way that it is used for estimating size (refer to Chapter 10), a regression-based model (we will look at COCOMO), a mathematical model (we will look at SLIM), and empirical models. This chapter will focus on the regression model and the mathematical model, and the formulas and tools that support them. No discussion of software sizing and estimating would be complete without mention of an empirical model from Software Productivity Research (SPR), a wholly owned subsidiary of Artemis Management

Systems and a leader in software estimation and planning. Led by software development luminary Capers Jones, SPR provides a tool, SPR

KnowledgePLAN , for software estimation and planning. It contains a project wizard that simplifies the process of developing estimates, a sizing wizard that walks users through the sizing process, a goals wizard that helps users identify and achieve key project goals, and templates that help the user quick-start a project. The name most commonly associated with COCOMO is Dr. Barry Boehm. Lawrence

Putnam, Sr., is associated with Quantitative Software Measurement (QSM, product is SLIM), and Capers Jones is associated with SPR

(KnowledgePLAN ). Each of these experts is considered to be among the top problem solvers in the software estimation and measurement field, has published multiple full-length texts and articles, and has collected data from thousands of software projects.

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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