Aim: To understand the processes that deal with the Project Schedule. Namely:
• Define Activities
• Sequence Activities
• Estimate Activity Resources
• Estimate Activity Durations
• Develop Schedule
Note: The processes above executed in the same order as they are listed above.
Any projects success depends on how well the activities were defined, sequenced and estimated. A good schedule is one that the team can comfortably stick to and work without slogging. The importance of proper planning cannot be emphasized enough.
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.
The table below shows the inputs, tools and techniques, and outputs for the define activities process.
| Define Activities | ||
|---|---|---|
| Inputs | Tools & Techniques | Outputs |
| Scope Baseline Enterprise Environmental Factors Organizational process assets | Decomposition Rolling wave planning Templates Expert judgment | Activity list Activity attributes Milestone list |
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.
You can learn more about Defining Activities by Clicking Here
Sequence Activities
The next process is that of arranging the activities list from activity definition into a proper 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.
The table below shows the inputs, tools and techniques, and outputs for the sequence activities process.
| Sequence Activities | ||
|---|---|---|
| Inputs | Tools & Techniques | Outputs |
| Activity list Activity attributes Milestone list Project scope statement Organizational process assets | Precedence diagramming method (PDM) Dependency determination Applying leads and lags Schedule network templates | Project schedule network diagrams Project document updates |
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.
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. 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
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.
Exam Watch:
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.
You can learn more about the PDM and Sequencing Activities by Clicking Here
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
The table below shows the inputs, tools and techniques, and outputs for the estimate activity resources process.
| Estimate Activity Resources | ||
|---|---|---|
| Inputs | Tools & Techniques | Outputs |
| Activity list Activity attributes Resource calendars Enterprise environmental factors Organizational process assets | Expert judgment Alternatives analysis Published estimating data Bottom-up estimating Project management software | Activity resource requirements Resource breakdown structure Project document updates |
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.
Exam Watch:You can learn more about the Estimate Activity Resources process by Clicking Here
In practical scenarios, most project managers are forced to create a schedule where the customer or the sponsor decides the go-live date and the manager is left to scramble for resources to ensure that the project is completed by that time. PMI does not expect you to think this way during the PMP Exam. Think of the ideal scenario where you have enough time to do either bottom-up or at least a top-down estimate done by an expert.
Estimate Activity Durations
After the resource estimates are identified/calculated for each of the activities, it’s time to assign duration estimates i.e., the time required to complete each of the activities for whom the resources were estimated in the previous step. 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.
The table below shows the inputs, tools and techniques, and outputs for the activity duration estimating process.
| Estimate Activity Durations | ||
|---|---|---|
| Inputs | Tools & Techniques | Outputs |
| Activity list Activity attributes Activity resource requirements Resource calendars Project scope statements Enterprise environmental factors Organizational process assets | Expert judgment Analogous estimating Parametric estimating Three-point estimates Reserve analysis | Activity duration estimates Project document updates |
• 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:
o Most likely (MT) -The duration most likely to occur.
o Optimistic (OT) -The duration of the activity based on analysis the best-case scenario.
o Pessimistic (PT) -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 (ET) activity from the three-point estimates using the following formula:
ET = (OT + 4*MT + PT) / 6
You can learn more about the Estimate Activity Durations process by Clicking Here
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 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.
The table below shows the inputs, tools and techniques, and outputs for the develop schedule process.
| Develop Schedule | ||
|---|---|---|
| Inputs | Tools & Techniques | Outputs |
| Activity list Activity attributes Project schedule network diagrams Activity resource requirements Resource calendars Activity duration estimates Project scope statement Enterprise environmental factors Organizational process assets | Schedule network analysis Critical path method Critical chain method Resource leveling What-if scenario analysis Applying leads and lags Schedule compression Scheduling tool | Project schedule Schedule baseline Schedule data Project document updates |
An important topic to understand with respect to project schedules is the critical path. 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.
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. It is assumed that all resources required for the activities are available on time. 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.
Float
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. 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.
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.
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 sick or resigns from the company? Such a question would be part of a what-if scenario.
You can learn more about the Develop Schedule process, with examples for the Network Diagram analysis by Clicking Here
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Next: Chapter 13
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