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Estimates Estimates Uncertainties Unknown Project development costs Project development schedules Team size Amount of software to be developed Hardware resources Estimates Estimation techniques Historical data Stepwise Estimation Counting product features Functional point Analysis Statistical application Construction Cost Model COCOMO Estimates Stepwise Estimation Divides a large problem into numerous smaller problems. The basic approach decomposes the project into well-defined components, then to iterate step-by-step until only small units remain, which can be easily estimated. Estimates Stepwise Estimation Project Decomposition Off-the-shelf components Full-experience components Partial-experience components New development Estimates Estimating New Development Prototype methods Statistical methods Estimates Charter Plan Pre-Launch Approval Launch Approval Execute Size Estimates (Macro) Task-based Estimates Project Schedule +/- 35% range +/- 15% range +/- 10% range Estimates Sizing techniques /models Used to generate high-level effort, duration, and cost projections at a point when little is known about the project Effort Distribution Models (EDM) Deliverables-Based Estimates Functional Point Estimating Models Used for new development mostly Estimates EDM Intial Study (IS) 2 User requirement (UR) 5 Conceptual design (CD) 12 External design (ED) 14 Internal design (ID) 19 Code & unit test (CUT) 26 System/acceptance test (SAT) 17 Instalation (IN) 3 Post-implementation (PI) 2 EDM System/accept ance test (SAT) Conceptual 17% Intial Study (IS) design (CD) User 2% 12% External design requirement (ED) (UR) 14% 5% Instalation (IN) Code & unit 3% test (CUT) Post- Internal design 26% implementation (ID) (PI) 19% 2% Estimation (EDM) Completed Phases Effort % Actual hours Intial Study (IS) 2 1426 User requirement (UR) 5 1949 Conceptual design (CD) 12 4138 19 7513 Future phases Effort Extrapolated effort External design (ED) 14 5536 Internal design (ID) 19 7513 Code & unit test (CUT) 26 10281 System/acceptance test (SAT) 17 6722 Instalation (IN) 3 1186 Post-implementation (PI) 2 791 Total 81 32029 Estimation (EDM) Converting effort hours into estimate durations. Convert the estimated phase effort hours to work months by dividing the total hours by the average production hours per month per person. 6.5 work-hours per day and 17.5 work-days per month Determine the Optimal Full-time Equivalent (OFTE) team members for each phase by taking the square root of the work months computed above Compute the estimated phase duration as Phase duration = work months / OFTE Develop a phase-base Gantt – depict the order of phase execution and appropriate phase overlaps and determine the duration estimate in terms of work-days, works weeks, or work-months. Problems Effort for user participation are usually not included A full-time PM for a 7 FTE team member. That is one FTE will consume 15% of PM’s time. Estimation (EDM) phases Work month Team OFTE Duration months PM FTE (ED) 5536/114 48.6 6.9 1 (ID) 7513/114 65.9 8.1 1.2 (CUT) 10281/114 90.2 9.5 1.4 (SAT) 6722/114 59 7.7 1.1 (IN) 1186/114 10.4 3.3 0.5 (PI) 791/114 6.9 2.7 0.4 Estimation (EDM) 0 month 10 months 20 months 30 months ED ID CUT SAT IN PI PM Effort 0 month 10 months 20 months 30 months ED ID CUT SAT IN PI Estimation (EDM) When to use EDM Medium to large projects Projects based on a well defined lifecycle methodology Major enhancements Size Estimate (Deliverables-based) Deliverables-based estimates Project description Project phases Project deliverables List of deliverables by phases Descriptions of deliverables Resource assumptions Number of resources, skill levels, percentage assignment Deliverable estimates (effort, cost, duration) Estimate project duration Size Estimate (Deliverables-based) Deliverables Sample list Approved vendor Data conversion plan Data definitions, data dictionary, etc Development strategy Disaster recovery plan Program specifications Regression test data Risk analysis Test plan, test data, etc Usability testing Training Size Estimate (Functional Point) Functional Point Estimate Used to size size system application from an end- user perspective. From business or logical point of view Independent of hardware, programming language, techniques, and tools used to developed the final system A functional point is defined as one end-user business function. The amount of functionalities in the project determines the project problems’ size. Size Estimate (Functional Point) FPA Problems Any functional point based estimate developed prior to the end of logical design are questionable FPA does not often consider non-business features of the systems e.g. Walk-throughs, inspections, team training, PM, etc Converting FP estimates into project duration and schedules can produce dubious results and lead to poorly defined plans Size Estimate (COCOMO model) COCOMO model Level of personnel PL = ƒ (∑EP,N, KSLOC) Level of complexity SEM = class of complexity * (KSLOC) Project size Reliability factor Development environment Task-based Estimate Task-based estimates Task effort The number of work hours needed to complete a given task. It depends on task complexity and skill of the person assigned to the task Task Duration Elapsed time needed to complete a given task. Measured in days, weeks, or months. Task-based Estimate Getting a reliable task-based estimate Ask the person to whom the task is assigned to estimate its duration The PM estimates the duration of various tasks, keeping in mind the team skill, knowledge, interruptions, and productivity environment The PM gathers a representative group of team members and they collectively estimate task effort and/or duration Use historical data from a similar project.
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