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Performing Top-down Estimation
Top-Down Estimation enables you to apply
In this chapter labor, nonlabor, and/or material resource units
to activities in a top-down manner using
Performing Top-down Estimation
assigned estimation weights.
Applying Saved Top-Down
Estimates To a Project
Read this chapter to learn how to perform and apply top-down estimation to WBS elements and activities.
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Performing Top-down Estimation
For information on assigning weights to WBS elements and activities, see “Reviewing Work Breakdown Structures” on page 133.
To perform top-down estimation, you must first assign estimation weights to work breakdown structure (WBS) elements and activities. You can assign estimation weights directly in the Project Management module or import them from the Methodology Management module using Project Architect.
You can limit the scope of your estimate according to work breakdown structure (WBS) element and resource. After you develop a top-down estimate, save the estimate for later reference or use, or apply the estimate to the project. If you apply an estimate, the module updates planned labor/ nonlabor units for all activities and activity resource assignments that fall within the estimation scope you specify. Top-down estimations do not affect project expenses.
When performing a top-down estimation, you should first determine the total number of labor or nonlabor resource units you want to apply. You can determine this number using either prior experience on similar projects, or you can use the module’s Function Point option, if you are estimating an information technology project.
Unlike labor and nonlabor resources, a top down estimate can not be applied to all material resources at once, because their units of measure differ. You must select the material resources individually.
For organizations using Primavera ProjectLink, top-down estimation is disabled for Microsoft Project (MSP)-managed projects. For more information on ProjectLink, click the Help button on any ProjectLink screen to access the help in Microsoft Project (available only if ProjectLink is installed).
Perform top-down estimations using prior experience Choose Tools, Top Down Estimation. Choose to estimate labor or nonlabor resource units. Click the Browse button in the WBS field to select the WBS element whose activities you want to estimate, then click the Select button. To estimate activities assigned to a specific resource within the specified WBS element, such as a material type resource, click the Browse button in the Resource field, select the resource, then click the Select button.
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The Total Activities field reflects the number of activities included under the specified WBS element.
To estimate the entire project, select the root WBS element.
Select an individual resource whose assigned activities you want to estimate for the selected WBS element.
Click to view detailed information about and/or apply a previously saved top-down estimate.
Choose Prior Experience. Using the value displayed in the Current Units field as a guide, type the estimate in the Estimated Units field. To apply an adjustment percentage to the estimate, mark the Apply Adjustment checkbox, then type the adjustment percentage you want to use. For example, if the estimated units are 400 and you apply an adjustment of 50%, the module will add 200 (50% of 400) to the estimated units. The Adjusted Units field will display 600 units.
To save the estimate without applying it, click Save As. Type a name and any assumptions and notes about the estimate, then click Save.
Develop top-down estimations using function points Choose Tools, Top Down Estimation. Choose to estimate labor or nonlabor resource units, or select a material resource in the Resource field. Click the Browse button in the WBS field to select the WBS element whose activities you want to estimate, then click the Select button. Choose Function Point, then click Function Points.
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Type the Unadjusted Function Point Count (UFP) value you want to use, or click Calculate to calculate the UFP.
If you choose to calculate the UFP, in the applicable boxes type the number of low, average, and high complexity files and transactions to be developed under the WBS element and resource, if any, you are estimating.
Click Close. The Function Point Estimation dialog box reappears. Your UFP value is listed in the Unadjusted Function Point Count (UFP) box.
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Type the Total Degree of Influence (TDI) value you want to use, or click Characteristics to calculate the TDI. If you choose to specify characteristics, select a system characteristic, then choose the numeric value that indicates the characteristic’s degree of influence on the WBS element you are estimating. A 0 indicates no influence and 5 indicates the strongest influence. When you select a value, the Value Description box displays text describing the value for the selected characteristic. Select a value for all system characteristics, then click Close.
The Function Point Estimation dialog box reappears. The TDI value is listed in the Total Degree of Influence (TDI) box.
Type the average productivity value, then click Close.
To apply an adjustment percentage to the estimate, mark the Apply Adjustment checkbox, then type the percentage you want to use. For example, if the estimated units are 400 and you apply an adjustment of 50%, the module will add 200 (50% of 400) to the estimated units. The Adjusted Units field will display 600 units.
To save the estimate without applying it, click Save As. Type a name and any assumptions and notes about the estimate, then click Save.
Apply top-down estimations Click Apply to perform the top-down estimation. Click Yes when prompted to confirm that you want to apply a top-down estimate to the project. Click OK.
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