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Estimation

Estimation. Chapter 3 Applied Software Project Management , Stellman & Greene. Decomposing a project into tasks. By feature By project phase Some combination. The most accurate estimates. Rely on prior experience Teams review previous project results Find how long previous projects took

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Estimation

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  1. Estimation Chapter 3 Applied Software Project Management, Stellman & Greene

  2. Decomposing a project into tasks • By feature • By project phase • Some combination

  3. The most accurate estimates... • Rely on prior experience • Teams review previous project results • Find how long previous projects took • Estimates will change because: • People leave the project/get sick • Technical problems arise • Needs of the organization change • The unexpected will almost certainly happen

  4. Two people may disagree on how long a task will take... • Generally because of assumptions on what is required • A good project manager can reduce the uncertainty by creating the vision and scope document

  5. Assumptions • Help when dealing with incomplete information • Should be written down and discussed • Brainstormed by team to identify as many assumptions as possible

  6. Questions to help identify assumptions • Are there project goals that are known to the team, but are not written down? • Are there any concepts, terms, or definitions that need to be clarified? • Are there standards that must be me, but will be expensive to comply with? • How will the development of this project differ from that of previous projects? Will there be new tasks added that were not previously performed? • Are there technology and architecture decisions that have already been made? • What changes are likely to occur elsewhere in the organization that could cause this estimate to be inaccurate? • Are there issues that the team is known to disagree on that will affect the project?

  7. Distrust can undermine estimates • Politics • “Rule” of cutting by third, half... • Lack of trust may cause engineers to inflate their estimates

  8. Wideband Delphi Estimation • Developed in 1940s by Rand Corp. for forecasting • This process produces: • Set of estimates for the schedule • WBS • List of assumptions (for Vision &Scope) • Discussion and time to correct each other • Depends on Vision and Scope document

  9. Delphi Process led by moderator • Kickoff meeting • Create WBS and list of assumptions • After the meeting each member creates an effort estimate for each task • Estimation session • Team revises estimates as a group and reaches consensus • Then project manager summarizes results and reviews with team • See Table 3-1

  10. Details... • Each team member must make an effort to estimate each task honestly • Free flow of information is essential • Sessions can get heated • Include observers to sit in on the meetings: stakeholders, users, managers

  11. Role of the moderator • Should ideally not have a stake in the project • Listens to discussion • Asks open-ended questions • Challenges team to address the issues • Ensures that everyone is contributing

  12. Kickoff meeting • Meeting activities • Moderator explains the process • All read the Vision and Scope if they have not • Moderator goes over the goal statement prepared by the PM and the moderator • Team discusses the product and brainstorms assumptions • Team generates a task list of ~10-20 major tasks => top level of WBS • Team agrees on units of estimation (days, weeks, pages, etc.) • WBS is generated

  13. Individual preparation • Each team member generates a set of preparation results as shown in Figure 3-1 • Task list with units of effort • Calendar waiting time • Project overhead tasks

  14. Estimation session • Members bring their individual work and ... • Fill out estimation forms as in Figure 3-2: one row for each task and totaled • Moderator collects and plots totals on a line: Figure 3-3 • Each estimator gives clarification and changes to the task list • Team resolves issues or disagreements • Estimators revise their estimates by filling in the next Delta column • Cycle repeats until agreement or two hours

  15. Assembling tasks and Reviewing results • Figure 3-5 shows each estimator’s final estimates • Best and worst cases are shown • Assumptions are put in final form and now entered into Vision and Scope • What happens when one team member continues to disagree?

  16. Other Techniques • PROBE • COCOMO II • The Planning Game • For Next Time: • Vision and Scope • Readings

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