Bài giảng Project Management - Chapter five: Estimating Project Times and Costs

5–2Where We Are Now5–3Estimating Projects EstimatingThe process of forecasting or approximating the time and cost of completing project deliverables.The task of balancing expectations of stakeholders and need for control while the project is implemented.Types of EstimatesTop-down (macro) estimates: analogy, group consensus, or mathematical relationshipsBottom-up (micro) estimates: estimates of elements of the work breakdown structure5–4Factors Influencing the Quality of EstimatesQuality of EstimatesProjectDurationPeopleProject Structure and OrganizationPaddingEstimatesOrganizationCultureOther (Nonproject)FactorsPlanning Horizon5–5Developing Work Package EstimatesPreparing Initial EstimatesUse several people to make estimatesAssume normal conditionsUse consistent time unitsAssume tasks are independentMake no allowance for contingenciesInclude a risk assessmentUse people familiar with the tasks5–6Top-Down versus Bottom-Up EstimatingTop-Down EstimatesAre usually derived from someone who uses experience and/or information to determine the project duration and total cost.Are made by top managers who have little knowledge of the processes used to complete the project.Bottom-Up ApproachCan serve as a check on cost elements in the WBS by rolling up the work packages and associated cost accounts to major deliverables at the work package level.5–7Estimating Projects: Preferred ApproachMake rough top-down estimates.Develop the WBS/OBS.Make bottom-up estimates.Develop schedules and budgets.Reconcile differences between top-down and bottom-up estimates5–8Top-Down Approaches for Estimating Project Times and CostsConsensus methodsRatio methodsApportion methodFunction point methods for software and system projectsLearning curvesProject Estimate Times Costs5–9Bottom-Up Approaches for Estimating Project Times and CostsTemplate methodsParametric procedures applied to specific tasksRange estimates for the WBS work packagesPhase estimating: A hybrid5–10Level of DetailLevel of detail is different for different levels of management.Level of detail in the WBS varies with the complexity of the project.Excessive detail is costly.Fosters a focus on departmental outcomesCreates unproductive paperworkInsufficient detail is costly.Lack of focus on goalsWasted effort on nonessential activities5–11Types of CostsDirect CostsCosts that are clearly chargeable to a specific work package.Labor, materials, equipment, and otherDirect (Project) Overhead CostsCosts incurred that are directly tied to an identifiable project deliverable or work package.Salary, rents, supplies, specialized machineryGeneral and Administrative Overhead CostsOrganization costs indirectly linked to a specific package that are apportioned to the project5–12Refining EstimatesReasons for Adjusting EstimatesInteraction costs are hidden in estimates.Normal conditions do not apply.Things go wrong on projects.Changes in project scope and plans.Adjusting EstimatesTime and cost estimates of specific activities are adjusted as the risks, resources, and situation particulars become more clearly defined.5–13Key TermsApportionment methodsBottom-up estimatesContingency fundsDelphi methodDirect costsFunction pointsLearning curvesOverhead costsPadding estimatesPhase estimatingRange estimatingRatio methodsTemplate methodTime and cost databases