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Analysis of Software Cost Estimation using COCOMO II
« on: August 20, 2011, 10:41:38 am »
Author : T.N.Sharma
International Journal of Scientific & Engineering Research Volume 2, Issue 6, June-2011
ISSN 2229-5518
Download Full Paper : PDF

Abstract - COCOMO II is an objective cost model for planning and executing software projects. It is an important ingredient for managing software projects or software lines of business. A cost model provides a framework for communicating business decisions among the stakeholders of a software effort. COCOMO II supports contract negotiations, process improvement analysis, tool purchases, architecture changes, component make/buy tradeoffs and several other return-on-investment decisions with a credible basis of estimate. COCOMO II incorporates several field-tested improvements to both broaden its applicability and improve its estimating accuracy for modern software development approaches. COCOMO II includes two underlying information models. The first is a framework for describing a software project, including models for process, culture, stakeholders, methods, tools and the size/complexity of the software product. The second is an experience base that can be used to estimate the likely includes significant updates to COCOMO to improve its applicability to modern processes, methods, tools and technologies. It also includes a much larger, more pertinent database of modern precedents and improves the adaptability of the model so it can be optimized across a broad spectrum of domains and project circumstances. This paper presents cost estimation of various projects using COCOMO II. This article also presents statistical analysis for relevance of base COCOMO II model for effort estimation in present scenario.
Index Terms— Software Cost Estimation, COCOMO II, Scale Factors, Cost Drivers, Case Studies.

1   INTRODUCTION                           
Software cost estimation is a prediction of the cost of the resources that will be required to complete all of the work of the software project.
Software has a bad reputation about cost estimation. Large software projects have tended to have a very high frequency of schedule overruns, cost overruns, quality problems, and outright cancellations. Instead of it bad reputation, it is important to note that some large soft-ware projects are finished on time, stay within their budgets, and operate successfully when deployed.

Currently a new generation of software processes and products is changing the way organizations develop software. The new approaches – evolutionary, risk driven and collaborative software processes; fourth generation languages and application generators; commercial off the shelf (COTS) and reuse driven software approaches; fast track software development approaches; software process maturity initiatives – lead to significant benefit in terms of improved software quality and reduced software cost, risk and cycle time.

COCOMO II model tailored to these new forms of soft-ware development, including rationales for the model decisions. The major new modeling capabilities of CO-COMO II are a tailorable family of software sizing mod-els, involving Object Points, Function Points, and Source Lines of Code; nonlinear models for software reuse and reengineering; an exponent-driver approach for modeling relative software diseconomies of scale; and several additions, deletions, and updates to previous COCOMO effort-multiplier cost drivers. This model is serving as a framework for an extensive current data collection and analysis effort to further refine and calibrate the model’s estimation capabilities.

In COCOMO II, the amount of effort in person-months, PM, is estimated by the formula:
The amount of calendar time, TDEV, it will take to develop the product is estimated by
      where F = D + 0.2 x 0.01 x ∑ SFj
           = D + 0.2 x (E – B)

In COCOMO-II effort is expressed as person month(PM). COCOMO II treats the number of person-hours per month, PH/PM, as an adjustable factor with a nominal value of 152 hours/PM.

•   The value of n is 16 for the Post-Architecture model effort multipliers, Emi, and 6 for the Early Design model, the number of SFi stands for exponential scale factors.
•   The values of A, B, C, D, SF1 …, and SF5 for the Early Design model are the same as those for the Post-Architecture model.

    Baseline Effort Constants:
A = 2.94;     B = 0.91
Baseline Schedule Constants:
C = 3.67;   D = 0.28


The application size is exponent is aggregated of five scale factors that describe relative economies or diseco-nomies of scale that are encountered for software pro-jects of dissimilar magnitude. 

•   Precedentedness(PREC)
•   Development Flexibility (FLEX)
•   Architecture / Risk Resolution (RESL)
•   Team Cohesion (TEAM)
•   Process Maturity (PMAT)

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