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Chapter 3. Examine Project Planning > Activity Planning—From WBS to Project Sch...

Activity Planning—From WBS to Project Schedule

  • Define Activities—6.1

  • Sequence Activities—6.2

  • Estimate Activity Resources—6.3

  • Estimate Activity Durations—6.4

  • Develop Schedule—6.5

CramSaver

If you can correctly answer these questions before going through this section, save time by skimming the Exam Alerts in this section and then completing the Cram Quiz at the end of the section.

1.Which type of network diagram allows you to depict four types of dependencies?

  1. Precedence diagramming method (PDM)

  1. Arrow diagramming method (ADM)

  1. Dependency diagramming method (DDM)

  1. Gannt chart diagram (GCD)


2.What term is defined as the practice of planning activities based on how soon the tasks are scheduled to start, such that activities that are close to their start date are planned at a more detailed level than those farther in the future? This term also implies that more detailed plans are required as activities approach their start date.

  1. Progressive elaboration

  1. Rolling wave planning

  1. Planning component elaboration

  1. Milestone detail planning


3.Which of the following statements best describes the estimate activity resources process?

  1. Identifying and documenting relationships among the project activities

  1. Identifying the specific actions to be performed to produce the project deliverables

  1. Estimating the number of work periods needed to complete individual activities

  1. Estimating the type and quantities of material, people, equipment, or supplies to perform each activity


4.Which estimating technique is best to use if you know the standard usage rate for a resource (such as an installer can pull 40 feet of cable per hour) to estimate the duration of an activity?

  1. Analogous estimating

  1. Parametric estimating

  1. Three-point estimates

  1. Reserve analysis


5.Which if the following is NOT a tool and technique for the develop schedule process?

  1. Critical path method

  1. Alternatives analysis

  1. What-if scenario analysis

  1. Applying leads and lags


Answers

1.Answer A is correct. The precedence diagramming method (PDM), also called Activity-On-Node (AON), supports finish-to-start, finish-to-finish, start-to-start, and start-to-finish dependencies. PDM is often used in critical path methodology (CPM). Answer B is incorrect because the arrow diagramming method (ADM) only allows for finish-to-start dependencies. Answers C and D are incorrect because they are not real diagramming methods.
2.Answer B is the best answer. Rolling wave planning is providing detailed plans for tasks that are starting in the near future by using the most current information and revisiting future activities as their starting dates approach. Although rolling wave planning is a type of progressive elaboration, it is mainly concerned with near-term activities. Answer A is not the best answer because progressive elaboration is the process of continuously improving a project plan as more is learned about the project. Answers C and D are incorrect because they are not valid project planning terms.
3.Answer D is correct. Estimate activity resources is the process of estimating the type and quantities of material, people, equipment, or supplies to perform each activity. Answer A is incorrect because it describes the sequence activities process. Answer B is incorrect because it describes the define activities process. Answer C is incorrect because it describes the estimate activity durations process.
4.Answer B is correct. Parametric estimating uses known historical data, such as production rates, to estimate duration. Answer A is incorrect because analogous estimating uses comparison with other, similar project work. Answer C is incorrect because three-point estimates use best, worst, and most likely estimates to calculated duration. Answer D is incorrect because is refers to the process of including contingency reserves into estimates, not actually calculating estimate durations.
5.Answer B is correct. Alternative analysis is a tool and technique for the estimate activity resources process. Estimate activity resources is the process of estimating the type and quantities of material, people, equipment, or supplies to perform each activity. Answers A, C, and D are all tools and techniques for the develop schedule process.


The next section of the planning processes address those steps required to develop the project schedule. This is the part of the project plan that might be most familiar to new project managers. Many automated project management tools help create schedules by keeping track of activities, resources, durations, sequencing, and constraints. Although the schedule is an integral part of the project plan, it is only one part. Don’t start working on the schedule until you have a proper WBS. Starting to work before completing the WBS nearly always results in doing more work than is necessary. A good WBS reduces task redundancy and helps ensure all work performed is in the scope of the project. In fact, the WBS is a required input to activity planning.

Define Activities

The first process in the activity planning section is define activities. This process starts with the WBS and identifies the activities required to produce the various project deliverables. Activities are viewed from the perspective of the work packages. You ask the question, “What activities are required to satisfy this work package requirement?” Next, the resulting information from this process is used to organize the activities into a specific sequence. Table 3.5 shows the inputs, tools and techniques, and outputs for the define activities process.

Table 3.5. Define Activities Inputs, Tools and Techniques, and Outputs
InputsTools and TechniquesOutputs
Scope baselineDecompositionActivity list
Enterprise environmental factorsRolling wave planningActivity attributes
Organizational process assetsTemplatesMilestone list
 Expert judgment 


Sometimes it is difficult to know everything about a project during the planning stage. It is common to learn more about the project as you work through the project life cycle. This is called progressive elaboration and affects the planning process. If you don’t know everything about the project, you can’t plan the whole project to the necessary level of detail.

For large projects, it is common to plan the entire project at a high level. The project starts with detailed plans in place for the work packages that are near the beginning of the project. As the time draws near to begin additional work, the more detailed, low-level plans for those work packages are added to the project plan. The planning process is revisited multiple times to ensure that the detailed plans contain the latest information known about the project. This practice is called rolling wave planning because the planning wave always moves to stay ahead of the work execution wave.

Sequence Activities

The next process is that of arranging the activities list from activity definition into a discrete sequence. Some activities can be accomplished at any time throughout the project. Other activities depend on input from another activity or are constrained by time or resources. Any requirement that restricts the start or end time of an activity is a dependency. This process identifies all relationships between activities and notes restrictions imposed by these relationships.

For example, when building a car you cannot install the engine until the engine has been built and delivered to the main assembly line. This is just one example of how activities can be dependent on one another. The sequence activities process is one that can benefit from the use of computer software to assist in noting and keeping track of inter-activity dependencies. Table 3.6 shows the inputs, tools and techniques, and outputs for the sequence activities process.

Table 3.6. Sequence Activities Inputs, Tools and Techniques, and Outputs
InputsTools and TechniquesOutputs
Activity listPrecedence diagramming method (PDM)Project schedule network diagrams
Activity attributesDependency determinationProject document updates
Milestone listApplying leads and lags 
Project scope statementSchedule network templates 
Organizational process assets  


Network Diagrams

One of the more important topics to understand when planning project activities is creating network diagrams. Network diagrams provide a graphical view of activities and how they are related to one another. The PMP exam tests your ability to recognize and understand the most common type of network diagrams: the precedence diagramming method (PDM). Make sure you can read a PDM and use the information it presents.

Figure 3.3 shows an example of a PDM diagram.

Figure 3.3. The precedence diagramming method.


Precedence Diagramming Method

The PDM shows nodes—representing activities—connected by arrows that represent dependencies. To represent that activity B is dependent on activity A (in other words, activity A must be complete before activity B starts), simply draw an arrow from A to B. PDM diagrams are also referred to as activity-on-node (AON) diagrams because the nodes contain the activity duration information. (We don’t have enough information to complete all the information presented here yet. We’ll fill in the duration information during activity duration estimating.) In fact, nodes generally contain several pieces of information, including

  • Early start— The earliest date the activity can start

  • Duration— The duration of the activity

  • Early finish— The earliest date the activity can finish

  • Late start— The latest date the activity can start

  • Late finish— The latest date the activity can finish

  • Slack— Difference between the early start and the late start dates

Figure 3.4 shows the sample PDM node template.

Figure 3.4. The sample PDM node template.
Early StartDurationEarly Finish
Task Name
Late StartSlackLate Finish


The PDM diagram in Figure 3.3 shows eight activities, labeled A through H, with 13 dependencies. The arrows show how some activities are dependent on other activities. For example, activity B cannot start until activities A and C are complete. To show this dual dependency, we draw an arrow from A to B and another arrow from C to B.

You can represent four types of dependencies with a PDM diagram:

  • Finish-to-start (the most common dependency type)— The successor activity’s start depends on the completions of the successor activity.

  • Finish-to-finish— The completion of the successor activity depends on the completion of the predecessor activity.

  • Start-to-start— The start of the successor activity depends on the start of the predecessor activity.

  • Start-to-finish— The completion of the successor activity depends on the start of the predecessor activity.

ExamAlert

Carefully consider the different types of dependencies. Some can be confusing (especially start-to-finish). On the exam, you are asked to evaluate the scheduling affect of changes in start or end dates. The overall effect to the project depends on the type of relationship between activities. Don’t skip over the dependencies too quickly. Take the time to really read the question before you construct your diagrams.


Project Task Information

After you are comfortable with the main types of network diagrams, you need to understand how to use them. Let’s talk about a few basic scheduling concepts and look at how network diagrams help you to understand project schedules, starting with a few project tasks. Table 3.7 lists the tasks for a project along with the predecessors, duration, and earliest start date.

Table 3.7. Project Task Information
ActivityPredecessorDurationEarliest Start Date
ANone59/5/09
BA29/10/09
CA39/10/09
DB79/12/09
EC49/13/09
FD19/19/09
GE, F29/20/09


Now use the sample PDM node template to create a PDM diagram for the project.

The completed network diagram should look like the diagram in Figure 3.5.

Figure 3.5. The completed sample PDM diagram.


Estimating Activity Resources

Now you have a list of activities and their relative dependencies. The next process associates activities with the resources required to accomplish the work. This process lists each type and amount, or quantity, of each required resource. Every activity requires resources of some sort. Activity resources can include

  • People

  • Equipment

  • Materials and supplies

  • Money

Table 3.8 shows the inputs, tools and techniques, and outputs for the estimate activity resources process.

Table 3.8. Estimate Activity Resources Inputs, Tools and Techniques, and Outputs
InputsTools and TechniquesOutputs
Activity listExpert judgmentActivity resource requirements
Activity attributesAlternatives analysisResource breakdown structure
Resource calendarsPublished estimating dataProject document updates
Enterprise environmental factorsBottom-up estimating 
Organizational process assetsProject management software 


Two of the tools and techniques warrant further discussion. One of the techniques you use when estimating activity resources is alternatives analysis. Analyzing the various alternatives provides an opportunity to consider other sources or ways to achieve the desired result for an activity. Alternatives might be more desirable than the initial expected approach due to cost savings, higher quality, or earlier completion. Another important outcome of alternative analysis is that in case the primary source becomes unavailable, you might have already identified a replacement method to complete the work. Suppose your main supplier of industrial fittings suffers a catastrophic fire. If your alternative analysis identified another source, you might be able to continue the project with minimal disruption.

The second item is bottom-up estimating. Recall that one of the purposes of creating the WBS is to decompose project work into work packages that are small enough to reliably estimate for duration and resource requirements. Using the WBS, you can provide estimates for mid- and high-level work by aggregating the estimates for the work packages that make up the desired work. Because this process starts at the lowest level of work (the work package) to create the estimate, it is called bottom-up estimating. This type of estimating tends to be fairly accurate because the estimates come from the people doing the actual work. The alternative is top-down estimating. Top-down estimates generally come from management or a source that is higher up than the people actually doing the work. The estimates are really educated guesses on the amount of resources required for a collection of work packages and tend to be less reliable than bottom-up estimates.

Estimate Activity Durations

After the resource estimates are established for each of the activities, it’s time to assign duration estimates. The estimate activity durations process approximates the number of work periods that are needed to complete scheduled activities. Each estimate assumes that the necessary resources are available to be applied to the work package when needed. Table 3.9 shows the inputs, tools and techniques, and outputs for the activity duration estimating process.

Table 3.9. Estimate Activity Duration Inputs, Tools and Techniques, and Outputs
InputsTools and TechniquesOutputs
Activity listExpert judgmentActivity duration estimates
Activity attributesAnalogous estimatingProject document updates
Activity resource requirementsParametric estimating 
Resource calendarsThree-point estimates 
Project scope statementsReserve analysis 
Enterprise environmental factors  
Organizational process assets  


In addition to expert judgment and reserve analysis, three main techniques are used for project activity duration estimation. In many cases, using multiple techniques provides more accurate estimates. The three estimation techniques are

  • Analogous estimating— This uses actual duration figures from similar activities. These activities can be from the same project or another project, but share similarities in budget, size, weight, complexity, or other parameters.

  • Parametric estimating— This calculates duration estimates by multiplying the quantity of work by the productivity rate. This type of estimate works best for standardized, and often repetitive, activities.

  • Three-point estimates— This uses three estimate values for each activity:

    • Most likely (tM)—The duration most likely to occur.

    • Optimistic (tO)—The duration of the activity based on analysis the best-case scenario.

    • Pessimistic (tP)—The duration of the activity based on the worst-case scenario.

This approach originated with the Program Evaluation and Review Technique (PERT). PERT analysis calculates the Expected (tE) activity from the three-point estimates using the following formula:

tE = (tO + 4 * tM + tP) / 6


Develop Schedule

The next step is to develop the actual project schedule. The develop schedule process pulls all of the activity information together and results in the project’s initial (baseline) schedule. As work is iteratively planned and accomplished and the project moves through its life cycle, changes to the schedule are likely to occur. The schedule is a dynamic document and requires constant attention on the part of the project manager to ensure the project stays on track. Table 3.10 shows the inputs, tools and techniques, and outputs for the develop schedule process.

Table 3.10. Develop Schedule Inputs, Tools and Techniques, and Outputs
InputsTools and TechniquesOutputs
Activity listSchedule network analysisProject schedule
Activity attributesCritical path methodSchedule baseline
Project schedule network diagramsCritical chain methodSchedule data
Activity resource requirementsResource levelingProject document updates
Resource calendarsWhat-if scenario analysis 
Activity duration estimatesApplying leads and lags 
Project scope statementSchedule compression 
Enterprise environmental factorsScheduling tool 
Organizational process assets  


An important topic to understand with respect to project schedules is the critical path. Refer to the AON diagram in Figure 3.3. The critical path is the longest path from start to finish. It is calculated by adding all of the durations along each path from start to finish. The reason it is called the critical path is that any delay (or increase in duration) of any activity on the critical path causes a delay in the project. It is critical that all activities on this path be completed on schedule.

Critical Path

Using the network diagram in Figure 3.5, you can calculate the project critical path. The critical path is the route with the longest total duration. The critical path method performs a forward and backward pass through the schedule network, calculating the early start and finish dates and the late start and finish dates for all activities, based on durations and relationships. The critical path method does not take resource limitations into account. The critical chain method does consider resource limitations. In short, the critical chain method uses the critical path method output and modifies the schedule network to account for limited resources. In this example, there are two routes from task A to task G:

  • Path A-B-D-F-G will take 17 days to complete. (Just add up all the durations: 5 + 2 + 7 + 1 + 2 = 17)

  • Path A-C-E-G will take 14 days to complete.

From this diagram, you can see that the longest path is A-B-D-F-G and that is your critical path. Any delays in any of these tasks delay the project.

Float

Refer to Figure 3.5. This PDM diagram has several pieces of information filled in for each node that we have not discussed. The task name and duration are self-explanatory. What about the rest of the information? The main task of developing the project schedule is to relate each of the tasks and combine duration, resource requirements, and dependencies. You need to make several passes through the network diagram to calculate the values necessary to create a project schedule.

In general, you make two main passes through each path in your network diagram. The first pass starts with the initial project task (the project “start” task). A task’s “early start date” is the earliest you can start working on that task. The “late start date” is the latest you can start working on the task. The difference between the early and late start dates is called float. The float is the schedule flexibility of a task. In Figure 3.5, the early start date for Task A is 9/5/09. To get the early finish date, just add the duration to the early start date. The duration for Task A is 5 days, so the earliest Task A can finish is 9/10/09. Now, the early finish date for Task A becomes the early start date for any tasks that are dependent on Task A (namely, Task B and Task C). Then, continue to follow each path until you reach the final task, calculating the new early end dates by adding the duration to the early start dates.

Note

Make sure you follow every path from the starting task to the ending task, calculating duration of each path. There are likely several paths that will get you there. Sometimes the shortest duration path might not be immediately evident.


Now it is time for the second pass through your project to calculate the late start and late ending dates. This pass starts at the end and moves backward through the same paths you just followed in the forward pass. The first step in the backward pass is to record the late ending date. It is the same as the early ending date for the last task in the project. Then, subtract the duration to get the late start date. In Figure 3.5, the late ending date for Task G is 9/22/09 and the late start date is 9/20/09. Next, move backward to each task on which your current task depends (that is each task that has an arrow pointing to your current task). The late ending date for this predecessor task is the same as the late start date of the dependent task. In other words, the late ending date for Task F and Task E would be 9/20/09, (the late start date for Task G). Continue backward through the project, subtracting the duration to calculate a new late start date.

After completing both the forward and backward passes, you should have all of the early start times (EST), early finish times (EFT), late start times (LST), and late finish times (LFT) filled in. To complete the network diagram entries, calculate the float for each task by subtracting the early start date from the late start date. The float represents the amount of time each task can be delayed without delaying the project.

Finally, add the durations for each path from the start task to the finish task. The smallest total represents the critical path of your project. There could be more than one critical path. Remember that tasks on the critical path all have a float of 0, and any delay of a task on the critical path results in an overall project delay.

Allocating Resources

In addition to calculating the critical path and critical chain, it might be necessary to address resource limitations. The process of reallocating resources that have been over-allocated is called resource leveling. This technique seeks to avoid work stoppage due to limited resources being required by multiple activities. Remember that resource leveling can often change the critical path. Because resource allocation can change the critical path it is often useful to implement another technique: what-if scenarios. The what-if scenario allows the project planners to explore the effect to the critical path of resource availability changes. For example, if you depend on a particular person to complete work on the critical path, what happens if that person becomes ill? Such a question would be part of a what-if scenario.

Cram Quiz

Answer these questions. The answers follow the last question. If you cannot answer these questions correctly, consider reading this section again until you can.

Use Figure 3.6 for questions 1, 2, and 3.

Figure 3.6. A sample PDM diagram.


1.What is the critical path for this project, and what is the duration of the critical path?

  1. A-B-D-F-G, 13 days

  1. A-C-E-G, 14 days

  1. A-B-D-F-G, 14 days

  1. A-C-E-G, 13 days


2.How many days can Task D be late in starting without affecting the project completion date?

  1. One day

  1. Two days

  1. Zero days

  1. Three days


3.If Task C starts two days late, what is the effect on the project end date?

  1. The project ends one day late because there is slack of one day.

  1. The project is still two days early because Tasks B, D, and F each have one day of slack.

  1. The project is one day late because Task C is on the critical path.

  1. There is no effect on the project end date.


4.When developing the estimates for project phases, you choose to add the individual estimates for the activities that comprise each phase. What type of estimation method are you using?

  1. Parametric estimating

  1. Bottom-up estimating

  1. Top-down estimating

  1. Analogous estimating


5.What is the primary purpose of the define activities process?

  1. Identify the specific actions to be performed that result in the stated project deliverables

  1. Identify and document relationships among project activities

  1. Analyze activity sequences, durations, resource requirements, and schedule constraints

  1. Monitor the status of the project schedule and manage schedule changes


6.Which estimating technique is the best choice if you know the durations of similar activities from other projects?

  1. Analogous estimating

  1. Parametric estimating

  1. Three-point estimating

  1. Historical analysis estimating


7.Which of the following is NOT an output of the develop schedule process?

  1. Project schedule

  1. Schedule baseline

  1. Schedule data

  1. Resource breakdown schedule


Cram Quiz Answers

1.Answer B is correct. The path A-C-E-G is the longest direct path from start to finish. All other answers are incorrect because they either state the incorrect path or project duration.
2.Answer A is correct. Because Task D is not on the critical path and has a slack of one day, it can start one day late (at most) without affecting the project end date.
3.Answer C is correct. Because Task C is on the critical path, any delay of the task delays the project.
4.Answer B is correct. Bottom-up estimating is the process of calculating estimates by aggregating the individual estimates of activities that make up the desired activity group. Answer A is incorrect because parametric estimating uses a process of multiplying quantity of work by the productivity rate. Answer C is incorrect because top-down estimating starts with an estimate and decomposes the estimate into smaller units to apply to the individual work packages. Answer D is incorrect because analogous estimating uses similar work packages, not estimate aggregation.
5.Answer A is correct. The stated answer is the main purpose of the Define Activities process. Answer B is incorrect because it states the purpose of the sequence activities process. Answer C is incorrect because it states the purpose of the develop schedule process. Answer D is incorrect because it states the purpose of the control schedule process.
6.Answer A is correct. Analogous estimating uses parameters from other similar activities to estimate durations. Answers B and C are incorrect because they refer to estimating techniques that do not consider similar activities. Answer D is incorrect because it refers to a estimating technique that doesn’t exist.
7.Answer D is correct. The Resource breakdown schedule is an output of the estimate activity resources process. Answers B, C, and D are incorrect because they are all valid outputs of the develop schedule process.

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