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CocomoPresentation - COCOMO Software Cost Estimating Model...

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COCOMO Software Cost Estimating Model Presentation by Paul T. Bathen For CIS6516 Management of Software Projects and Personnel” Summer B, 2008
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Outline of Presentation Brief overview of versions. Summary of email from Kurt Bittner. Cocomo 81; demonstration Cocomo II; demonstration CoStar by SoftStarSystems.com; demo
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COCOMO Versions CO (Constructive) CO (Cost) MO (Model) First version: 1981 by Dr. Barry Boehm Now known now as “COCOMO 81” Second version: ADA Cocomo (ADA 87); parameterized exponent reflecting more modern practices and their economies of scale. Current Version: Cocomo II (circa 2000) Commercial take-offs Costar (Softstarsystems.com) Cost Xpert (CostXpert.com) Regression formula, with data taken from historical projects and current project characteristics.
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Email from Kurt Bittner “Is COCOMO II best for iterative process?” Yes. “(the models are) public, have evolved over almost two decades, and are based on solid, proven research with solid data.” Caveat: COCOMO II models are “post- architectural” (best for Construction phase). (PTB Note: Cocomo II software allows for calculating and reporting by Early Design and Post Architecture)
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Bittner email cont’d Inception phase: driven by business/exploratory technology issues; generally defies estimation (because so little data exists at the beginning of a project). Elaboration phase: driven by technical risks and exploration of technology issues. Transition phase: not largely governed by software economics but is affected by a large number of factors other than software development.
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Cocomo 81 Accuracy Cocomo homepage: “Over 63 data points in the COCOMO 81 calibration database, the Intermediate form demonstrates an accuracy of within 20% of actuals 68% of the time for effort, and within 20% of actuals 58% of the time for a non-incremental development schedule.” Kemerer 1993: “(estimating in general varies) from as much as 85 - 610 % between predicated and actual values. Calibration of the model can improve these figures, However, models still produce errors of 50-100%.” Source: http://yunus.hacettepe.edu.tr/~sencer/cocomo.html
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Cocomo 81 Three calculation models: Basic : single-variable static model • Effort in staff months = C1 b * (KDSI) P1 Schedule in total months= C2 * (Effort) P2 Intermediate : Two variables. • Effort in man months = C1 i * EAF * (KDSI) P1 Schedule in total months = C2 * (Effort) P2 EAF = E1 * E2 * … E15 Detailed : Intermediate + assessed per phase (analysis, design, etc)
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Cocomo 81 • C1 i * EAF * (KDSI) P1 AND C2 * (Effort) P2 • C1 b , C1 i : Scaling coefficient for effort C2: Scaling coefficient for schedule EAF: Effort Adjustment Factor; 15 parameters covering Product, Personnel, Computer, and Project familiarity. P1: characterization of economies of scale: ability
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CocomoPresentation - COCOMO Software Cost Estimating Model...

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