項目管理雙語教學課件：PM5 Estimating Project Times and Costs

1、Project Management - 5Estimating Project Times and CostsContent & objectivesTo understand estimating project times and costs To have an awareness of the methods, uses, and advantages and disadvantages of macro and micro estimating methodsTo understand the need for time-phasing budgetsTo understand t

2、he different types of costs used to compute total project costSuggest estimating guidelines for time, cost and resourcesTo suggest a scheme for developing an estimating database for future projects Estimating Projects EstimatingThe process of forecasting or approximating the time and cost of complet

3、ing project deliverables.The task of balancing the expectations of stakeholders and the need for control while the project is implementedTypes of EstimatesTop-down (macro) estimates: analogy, group consensus, or mathematical relationshipsBottom-up (micro) estimates: estimates of elements of the work

4、 breakdown structure Why Estimating Time and Cost Are ImportantEstimates are needed to support good decisions.Estimates are needed to schedule work.Estimates are needed to determine how long the project should take and its cost.Estimates are needed to determine whether the project is worth doing.Est

5、imates are needed to develop cash flow needs.Estimates are needed to determine how well the project is progressing.Estimates are needed to develop time-phased budgets and establish the project baseline. Factors Influencing the Quality of EstimatesQuality of EstimatesProjectDurationPeopleProject Stru

6、cture and OrganizationPaddingEstimatesOrganizationCultureOther (Nonproject)FactorsPlanning Horizon Estimating Guidelines for Times, Costs, and ResourcesHave people familiar with the tasks make the estimate.Use several people to make estimates.Base estimates on normal conditions, efficient methods, a

7、nd a normal level of resources.Use consistent time units in estimating task times.Treat each task as independent, dont aggregate.Dont make allowances for contingencies.Adding a risk assessment helps avoid surprises to stakeholders. Macro versus Micro EstimatingConditions for Preferring Top-Down or B

8、ottom-up Time and Cost EstimatesCondition Macro Estimates Micro EstimatesStrategic decision making X Cost and time important XHigh uncertainty XInternal, small project XFixed-price contract XCustomer wants details XUnstable scope X Estimating Projects: Preferred ApproachMake rough top-down estimates

9、.Develop the WBS/OBS.Make bottom-up estimates.Develop schedules and budgets.Reconcile differences between top-down and bottom-up estimates Methods for Estimating Project Times and CostsMacro (Top-down) ApproachesConsensus methodsRatio methodsApportion methodFunction point methods for software and sy

10、stem projectsLearning curvesProject EstimateTimesCosts Apportion Method of Allocating Project Costs Using the Work Breakdown Structure Simplified Basic Function Point Count Process for a Prospective Project or Deliverable Example: Function Point Count Method Methods for Estimating Project Times and

11、Costs (contd)Micro (Bottom-up) ApproachesTemplate methodParametric Procedures Applied to Specific TasksDetailed Estimates for the WBS Work PackagesPhase Estimating: A Hybrid SB45 Support Cost Estimate Worksheet Phase Estimating over Product Life Cycle Level of DetailLevel of detail is different for

12、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 activities Developing

13、 BudgetsTime-Phased BudgetsA cost estimate is not a budget unless it is time-phased.Time phasing begins with the time estimate for a project.Time-phased budgets mirror how the projects cash needs (costs) will occur or when cash flows from the project can be expected.Budget variances occur when actua

14、l and forecast events do not coincide. Work Package Estimates Three Views of Cost Types 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 proje

15、ct 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 project Contract Bid Summary CostsDirect costs $80,000Direct overhead $20,000G&A overhead (20%)

16、 $20,000Profit (20%) $24,000Total bid $144,000 Refining 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 ar

17、e adjusted as the risks, resources, and situation particulars become more clearly defined. Refining Estimates (contd)Contingency Funds and Time BuffersAre created independently to offset uncertainty.Reduce the likelihood of cost and completion time overruns for a project.Can be added to the overall

18、project or to specific activities or work packages.Can be determined from previous similar projects.Changing Baseline Schedule and BudgetUnforeseen events may dictate a reformulation of the budget and schedule. Creating a Database for EstimatingEstimating Database Templates Key TermsApportionment methodsContingency fundsDelphi methodDirect costsFunction pointsInteraction costsLearning curvesMacro and micro estimatingOverhead costsPadding estimatesPhase estimatingRatio methodsTemp