On the Sensitivity of COCOMO II Software Cost Estimation Model

  • Authors:
  • Petr Musilek;Witold Pedrycz;Nan Sun;Giancarlo Succi

  • Affiliations:
  • -;-;-;-

  • Venue:
  • METRICS '02 Proceedings of the 8th International Symposium on Software Metrics
  • Year:
  • 2002

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Abstract

Software cost estimation techniques predictthe amount of effort required to develop asoftware system. Cost estimates are neededthroughout the software lifecycle to determinefeasibility of software projects and to provide forappropriate allocation or reallocation of availableresources. As the cost of a project depends on thenature and characteristics of the project, theaccuracy of the estimates depends on the amountof reliable information about the product to bedeveloped. At the same time, most costestimation models rely heavily on subjectiveexpert evaluations affected by possibly highdegree of imprecision and uncertainty. To assessthe effect of imprecise evaluations, acomprehensive sensitivity analysis has beenperformed on a major cost estimation model,COCOMO II. Results of this analysis aredescribed and explicated in this paper. To reducerisk of drawing biased conclusions, threedifferent methods for sensitivity analysis havebeen employed: mathematical analysis of theestimating equation, Monte Carlo simulation,and error propagation. The results of the first twomethods are very consistent and confirmexpected highest sensitivity of the model to theimprecision of the size estimate. Errorpropagation allows determination of thecombined impact of imprecision in multipleinputs and it is therefore most valuable from thepractical point of view. The results obtained bythis technique also indicate very strongsensitivity to the imprecision in size estimates. Apossible way to cope with imprecise informationin software cost estimation is indicated in theconcluding part of the paper.