Why bother creating a wbs? why not go straight to a project network and forget the wbs?

Chapter 6

developing a project plan

Review Questions

1. How does the WBS differ from the project network?

a. The WBS is hierarchical while the project network is sequential.

b. The network provides a project schedule by identifying sequential dependencies and timing of project activities. The network sets all project work, resource needs, and budgets into a sequential time frame; the WBS does not provide this information.

c. The WBS is used to identify each project deliverable and the organization unit responsible for its accomplishment within budget and within a time duration.

d. The WBS provides a framework for tracking costs to deliverables and organization units responsible.

2. How are WBS and project networks linked?

The network uses the time estimates found in the work packages of the WBS to develop the network. Remember, the time estimates, budgets, and resources required for a work package in the WBS are set in time frames, but without dates. The dates are computed after the network is developed.

3. Why bother creating a WBS? Why not go straight to a project network and forget the WBS?

The WBS is designed to provide different information for decision making. For example, this database provides information for the following types of decisions:

a. Link deliverables, organization units, and customer

b. Provide for control

c. Isolate problems to source

d. Track schedule and cost variance. Network doesn’t.

e. Assign responsibility and budgets

f. Focus attention on deliverables

g. Provide information for different levels in the organization.

4. Why is slack important to the project manager?

Slack is important to the project manager because it represents the degree of flexibility the project manager will have in rearranging work and resources. A project network with several near critical paths and hence, little slack, gives the project manager little flexibility in changing resources or rearranging work.

5. What is the difference between free slack and total slack?

Free slack usually occurs at the end of an activity chain—before a merge activity. It is the amount of time the activity can be delayed without affecting the early start of the activity immediately following it. Since free slack can be delayed without delaying following activities, it gives some resource flexibility to the project manager. Total slack is the amount of time an activity can be delayed before it becomes critical. Use of total slack prevents its use on a following activity.

6. Why are lags used in developing project networks?

Two major reasons:

a. To closer represent real situations found in projects

b. To allow work to be accomplished in parallel when the finish-to-start relationship is too restrictive.

7. What is a hammock activity, and when is it used?

A hammock activity is a special purpose activity that exists over a segment of the life of the project. A hammock activity typically uses resources and is handled as an overhead cost—e.g., inspection. Hammock activities are used to identify overhead resources or costs tied directly to the project. The hammock duration is determined by the beginning of the first of a string of activities and the ending of the last activity in the string. Hammock activities are also used to aggregate sections of projects to avoid project detail—e.g., covering a whole subnetwork within a project. This approach gives top management an overview of the project by avoiding detail.

Exercises

Drawing AON Networks

2.

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3.

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4.

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AON Network Times

7.

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8.

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9.

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Lag Exercises

17.

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19.

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20.

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Case

Greendale Stadium Case

The entry table is presented in GB-1 while the Gantt chart for the estimated schedule is presented in GB-2. GB-3 contains the schedule table which features Free and Total Slack.

MS Project files generated for this exercise can be found either on the teacher’s CD-Rom or at the Instructional Support Web Site.

Assignment:

1. Will the project be able to be completed by the May 20 deadline? How long will it take?

The project is estimated to take 695 days and be completed by March 27, 2009. This is 54 calendar days ahead of schedule.

2. What is the critical path for the project?

There are two interwoven critical paths:

· Clear Stadium Site ( Drive Support Piles ( Pour Lower Concrete Bowl ( Pour Main Concourse ( Install Seats ( Construct Steel Canopy ( Light Installation ( Inspection.

· Clear Stadium Site ( Drive Support Piles ( Pour Lower Concrete Bowl ( Construct Upper Steel Bowl ( Install Seats ( Construct Steel Canopy ( Light Installation ( Inspection.

3. Based on the schedule would you recommend that G&E pursue this contract? Why? Include a one-page Gantt chart for the stadium schedule.

The answer should be “yes” since there is a 54 day buffer between estimated completion date and the deadline. Furthermore, even though the network is sensitive with two critical paths, these paths involve only two separate activities. Some students will point out that over-time and working on weekends could be used to stay on schedule if delays occur.

A few students may argue that G&E can endure limited penalty costs given the profit margin for the project. While there is some truth to this logic, the loss of future business due to damaged reputation is a strong counter argument against this line of reasoning.

GB-1

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GB-2

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GB-3

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Appendix Review Questions

1. How do the building blocks of AON and AOA differ?

The building blocks of AON and AOA are the arrow and the node. However, AON uses the node to depict an activity, while the AOA uses the arrow to depict an activity. Recall activities consume project time. In both cases the arrow is used to indicate dependencies among activities. AOA uses the node to represent an event, which does not consume time. The AOA node marks the beginning or end of a project activity and can be used as a common beginning or ending event for several activities.

2. What are the purposes of dummy or pseudo activities?

The purpose of a dummy or pseudo activity is to maintain the logic of an AOA network and ensure each activity has its own unique identification number.

3. How do activities differ from events?

Activities consume time while events do not. The latter represent an instant in time when an activity begins or ends.

Appendix Exercises

1. Exercise 3

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Exercise 4

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Chapter 6 Developing a Project Plan 113

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