Establishing project schedules

Text by Stanley E. Portny, Samuel J Mantel, Jack R. Meredith, Scott M. Shaffer, Margaret M. Sutton with Brian Kramer.

PowerPoints by Christine Mooney

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Network Diagrams

Project managers and staff often feel they do not have enough time to complete a project.

The total time required to perform a group of activities depends on duration (how long) & sequence (order of activities).

Project managers can use network diagrams to assist them in completing activities.

Network Diagram – is a flow chart that illustrates the order in which activities need to be performed in a project. It includes three elements:

1. Event 2. Activity 3. Time span

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Elements of Network Diagrams

• Event – A significant occurrence in the life of the project; also called a milestone.

• Activity – Work required to move from one event to the next in a project.

• Span Time – The actual calendar time required to complete an activity; also called duration or elapsed time.

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Network Diagram Options

• Network diagrams can be drawn in two formats: activity on the arrow or activity in the box. Project managers also add the following terms to flow charts:

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Precedence diagram – another term for activity-in-the-box

Dependency Diagram – another term for network diagram

CPM charts – stands for critical path methods, uses estimates to allow time/cost trade-offs to be used.

PERT chart – a network diagram following activity-on-the-arrow.

Gantt chart – used for illustrating schedules

In addition, both CPM and PERT use slightly different ways of drawing the network of activities.

Activity-on-the-Arrow

• The activity-on-the-go uses distinct symbols to describe each of the elements of the diagram.

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A activity-in-the-box

The activity-in-the-box approach uses only two symbols to describe the three elements of the diagram.

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Selecting a Network Diagram

• Despite the similarities of diagramming formats, a project manager should consider the following:

a. The activity-on-the-arrow approach represents each element with a unique symbol.

b. The activity-in-the-box approach allows a project manager to draw out an entire project without defining any events.

c. The more commonly used and integrated project management software packages use the activity-in-the-box approach.

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Analyzing network diagrams

The following rules should be used in interpreting network diagrams:

Rule 1 – After someone finishes an activity or reaches an event, he/she can proceed to the next activity as indicated by the arrows.

Rule 2 – To be able to start an activity or reach an event, someone must complete all activities and reach all events from which arrows entering that activity or event emanate.

Network diagrams help project managers determine the following information and figure out what schedules are possible:

a. Critical path b. Noncritical path c. Slack time d. Earliest start date

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Determining Paths & Dates • A project manager’s first step in analyzing a

network diagram is to start at the beginning of the project and see how fast the project can be completed along each path of the project until reaching the conclusion. This start to finish analysis is called forward pass.

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Determining Times & Dates

• Determining critical paths and earliest start and finish dates is only half of a project manager’s responsibilities. They also need to determine how much they can delay the activities along each path of a project and still finish the project at the earliest possible date. This finish to start activity is called backward pass.

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Sequencing

• A project manager must decide the sequence in which a project’s activities will be performed.

• A predecessor is an activity you must complete before someone can work on another activity.

• An immediate predecessor is a term given to activity that, upon completion can allow someone to start on the following activity.

• Project managers should determine the immediate predecessors for every activity in a project based on the information available in the project’s network diagram.

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Relationships between activities

• Relationships between activities are based on several considerations:

a. Required relationships – relationships that must be observed if project work is to be successfully completed.

b. Legal requirements – compliance with local and state laws.c. Procedural requirements – company policies and procedures d. Discretionary relationships – a project team may choose to

establish a relationship with certain parties.

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Parkinson’s Law

• Project managers making time estimates need to remember and incorporate Parkinson’s law in their time estimates.

• Parkinson’s law states that work will expand to fill the amount of time allotted.

• For example, Jean says an activity will take 40 hours to complete, although the work could be finished in 28 hours.

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Developing Project Schedules

Project managers can complete a first draft of a project schedule by using the following steps: describe the objectives, detail the activities, identify immediate predecessors, estimate span times, identify intermediate and final dates that must be met.

Project managers need to be aware of developing schedules by backing in. Backing in is the process of starting at the end of a project and working back toward the beginning, identifying activities and estimating durations that eventually will add up to the amount of time the project has been given.

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Meeting Time Constraints

• If a project manager must complete a project in less time than the initial schedule, he can consider the following for all critical path activities:

a. Recheck the original span time estimates.

b. Consider using more experienced personnel

c. Consider different strategies for performing them

d. Fast tracking

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Project Success A project manager sometimes will change the criterion for

success from achieving a desired result, where it belongs, to performing a series of activities, where it does not.

The success of the picnic-at-the-lake project is arriving at the lake for the picnic, not performing a predetermined set of activities.

A project manager should always explore all sequence options.

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Estimating Activity Duration

A span time estimate is a project manager’s best sense of how long it will actually take to perform an activity.

When estimating an activity’s time span, project manager’s should describe the project’s components.

A project manager may need additional resources. Like equipment, personnel and raw materials. A project manager may need fudge time. A time to make necessary adjustments to a project.

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Formats to Present Project Schedules

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Key-events report A table that lists events and the dates on which you plan to reach them.

Activities report A table that lists activities and the dates on which you plan to start and end them.

Gantt chart A graph illustrating on a timeline when each activity will start, be performed, and end.

Combined Milestone chart & Gantt chart

A graph illustrating on a timeline when activities will start, be performed, and end, as well as when selected events will be achieved.

Precedence Diagramming

• Precedence diagram is another term for a network diagram in the activity-in-the-box format.

• With precedence diagramming, activities may be linked in the following ways:

a. Finish to start linkage b. Start to start linkage c. Finish to finish linkaged. Start to finish linkage

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