PM-P3

MGT 6305, Project Management 1

Course Learning Outcomes for Unit III Upon completion of this unit, students should be able to:

2. Determine project scheduling techniques. 2.1 Determine plan schedule management including the define activities, activity durations, and

sequence activities. 2.2 Plan the project schedule using the network diagram.

Course/Unit Learning Outcomes

Learning Activity

2.1, 2.2 Unit Lesson Chapter 9 Unit III Project

Required Unit Resources Chapter 9: Project Scheduling: Networks, Duration Estimation, and Critical Path It is not required to read the solved problems or the case studies at the end of the chapter.

Unit Lesson

Plan Schedule Management Process The project requirements have been collected and analyzed, and the project scope is defined. The question for the project manager now is: “what next?” The next step is to develop the project schedule. The schedule will inform the project team how long it will take to produce the project deliverables. Also, resources are assigned to the activities in the schedule, and resources are usually the primary source of project costs. For this reason, once all activities are in place and resources are assigned, the overall budget picture emerges. Before developing the schedule, just as in the case of project scope, it is good practice to take a step back and carefully consider the strategy for developing and managing the project schedule. This is the plan schedule management process. Plan schedule management will answer questions such as:

• How will activities required to produce project deliverables be defined?

• Who will be responsible?

• What techniques will be used for estimating the level of effort required for each activity?

• How will activity durations be estimated?

• What schedule development, management, and control tools or applications will be employed?

Answers developed for questions such as these lead to the schedule management plan. This plan will become the strategy referred to throughout the development and management of the project schedule.

UNIT III STUDY GUIDE

The Project Schedule

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Define Activities The definition of project activities begins by referring to the work breakdown structure (WBS) created in the development of the project scope. As an example of how this is done, consider the WBS element Exterior (Figure 1) and the underlying element Foundation that was depicted in one leg of the WBS created in the previous unit.

Figure 1 The foundation element of the WBS is a deliverable. The project manager will take this deliverable and consider what tasks or activities will be required to create this deliverable. This can be carried out easily by taking the indented outline of the WBS created in Excel (or imported into a project management software application) and layering in the associated activities. This has been carried out in the example below by adding the activities survey property, level area, map out plot, frame foundation area, lay rebar, and pour concrete (see Figure 2 below).

2.0 Exterior

2.1 Foundation

- Survey property

- Level area

- Map out plot

- Frame foundation area

- Lay rebar

- Pour concrete Figure 2. The subsections of exterior foundation section

The activity definition process continues until all activities required to produce project deliverables are in place. Having done this, it is time to move on to the determination of activity durations. Assess Activity Durations How long will any given project activity take? There are many ways for a project team to think about this and estimate activity durations. A common approach is to consider similar activities from similar projects. This may work if the activities in the current project are very similar or exactly the same as previous projects. This is not always the case, and appearances can be deceiving. For example, in complex systems and information technology projects, standards, tools, and technologies can change significantly from project to project. This is less of an issue for a home-building project unless there is something unusually challenging in the design or the type of materials employed. When activity durations are well-known, for example, the time it takes to install a standard size window, a fixed duration may be assigned. However, if the duration is known to vary, three durations are assigned

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instead of one. These are known as three-point estimates, and they are done using the optimistic duration estimate, a most likely estimate, and finally a pessimistic estimate. The three estimates must be combined in some way so that they may be assigned to an activity in the project schedule. This is done most frequently in project management by creating a weighted average that follows what is known in statistics as the beta distribution. While this sounds complicated, it is simple to implement in practice, and knowledge of the underlying statistics is not necessary. The formula for combining three-point estimates is as follows (Pinto, 2019):

(Pessimistic estimate + (4  Most likely estimate) + Optimistic estimate) ÷ 6

To illustrate how this calculation is performed in practice, consider the duration estimate for pouring concrete. If the optimistic time is 45 minutes, the most likely is 60 minutes, and the pessimistic time is 90 minutes, then the duration assigned to pour concrete is:

(45 + (4 x 60) + 90) ÷ 6 = 62.5 minutes

Why combine three-point estimates in this way? First, the calculation results in a single duration estimate to assign to an activity when the exact time is uncertain. Second, the formula employed includes optimistic and pessimistic figures while placing emphasis on the most likely estimate. Finally, the figure that results is in effect a weighted average. When averages or, more technically termed, means are employed as duration estimates, this supports the calculation of probability of achieving specific schedule target dates. Such calculations may not be carried out when fixed estimates are used. Sequence Activities Projects will include activities that occur one after another in sequence as well as activities that will be carried out at the same time in parallel. Using the homebuilding example, the framing of the home cannot begin until the foundation has been poured and set. Likewise, the interior cannot be completed until the roof is installed. However, once the roof is in place, many activities may be carried out in parallel. For example, the construction team may put in plumbing and electrical in parallel, since there are no obvious constraints requiring one to be done prior to another. When one activity occurs prior to another activity, the activity that occurs before is known as a predecessor activity. When an activity follows another activity, the following activity is referred to as a successor.

Program Evaluation and Review Technique, Critical Path Method, and Network Diagrams Because project activities occur both in series as well as in parallel, it is usually not possible to simply add up all project activity durations and consider the sum to be the total duration of the project. Each of the activities must be arranged in a diagram so that the activities, activity durations, and finally, the sequence of activities— both serial and parallel—may be observed. This diagram is known as a network diagram. When a network diagram is used to determine the overall duration of the schedule, this is known as the CPM or the Critical Path Method. The term critical path is the longest path in the diagram and the shortest possible duration in which the project may be completed (Marion, 2019). The CPM is also referred to as the PDM or Precedence Diagramming Method, as well as the PERT or Program Evaluation and Review Technique. The CPM and PERT operate exactly the same in terms of evaluating the network diagram. However, the PERT employs the weighted average of the three-point estimates for each activity duration, whereas the CPM does not. Calculating the schedule duration using a network diagram is carried out using the following steps—using the activities for the foundation of the WBS deliverable.

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Numbered Activities List For the foundation of the WBS deliverable, the identified activities are as follows.

Number Activity

1 Survey property

2 Level area

3 Map out plot

4 Frame foundation area

5 Lay rebar

6 Pour concrete

Table 1: Activities Activity Durations Given that the activity durations associated with the foundation are known to vary, the durations are calculated using the weighted average of three-point estimates (in hours), see Table 2.

Number Activity Optimistic Most Likely Pessimistic W-Average

1 Survey property 24 36 54 37

2 Level area 12 15 18 15

3 Map out plot 8 10 15 10.5

4 Frame foundation area 8 12 15 11.83

5 Lay rebar 4 8 12 8

6 Pour concrete 8 10 15 10.5

Table 2: Activity Durations Identify Predecessors For the purposes of the example, assume that framing of the foundation area and the lay rebar activity may be completed in parallel, see Table 3.

Number Activity Optimistic Most Likely

Pessimistic W- Average

Predecessor

1 Survey property

24 36 54 37 None

2 Level area 12 15 18 15 1

3 Map out plot 8 10 15 10.5 2

4 Frame foundation area

8 12 15 11.83 3

5 Lay rebar 4 8 12 8 3

6 Pour concrete 8 10 15 10.5 4 and 5

Table 3: Identify Predecessors

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Create Network Diagram Once activities, activity durations, and predecessors are in place, the network diagram is created. Each activity in the network diagram is typically identified using a box with nine squares that identify the activity, identify the early start (ES), early finish (EF), late start (LS), late finish (LF), and slack (SL). These labels are used for determining the overall schedule duration using the forward and backward pass calculation.

Forward Pass The forward pass begins at the first activity (Time 0) and adds durations from each activity. The end of one activity is the beginning of the next activity that follows. In the case of parallel activities that follow another activity (in this case Activity 3 and 4 following Activity 2), both 3 and 4 begin after Activity 2 ends. Beginning with activity 1, the start time is added to the duration so as to arrive at the finish time. For activity one, this is 37. This duration becomes the starting time for the next activity—and this continues until the final activity is reached.

Notice however that Activity 3 and 4 end at different times. But when should Activity 5 begin? Activity 5 begins once both Activities 3 and 4 end. This means in practice that Activity 5 begins after the longest of preceding activities end. This is Activity 4, so Activity 5 begins once Activity 4 ends.

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Backward Pass The backward pass begins at the end of the network diagram and works forward. The backward pass reverses the process carried out in the forward pass. The final duration is the starting point, and the duration of the final activity is subtracted from this total. This continues through all activities in the schedule until the beginning activity is reached.

What is the point of the network diagram and the forward and backward pass analysis? This exercise identifies the critical path—the path that has activities with zero slack. Slack is calculated by subtracting ES from LS (or vice versa). Activities with zero slack are found on the critical path. The critical path duration is the duration of the schedule. Also, if any activity on the critical path is delayed, the entire schedule is delayed. In the case of the foundation schedule, the duration is determined to be 82.33 hours. Finally, the critical path may now be determined by inspection—Activities 1, 2, 4, 5, and 6.

References Marion, J. W. (2019). Project management: A common-sense guide to the PMBOK program, part two–plan

and execution. Momentum Press. https://libraryresources.columbiasouthern.edu/login?url=https://search.ebscohost.com/login.aspx?dire ct=true&db=e000xna&AN=1918052&site=ehost-live&scope=site

Pinto, J. K. (2019). Project management: Achieving competitive advantage (5th ed.). Pearson.

https://online.vitalsource.com/#/books/9780134730509

Suggested Unit Resources In order to access the following resources, click the links below. Review the Chapter 9 PowerPoint Presentation to supplement the textbook reading and lesson content. You can also view a PDF version of the Chapter 9 presentation.