Developing the Critical Path in MS Project
The total duration of the project is determined by the duration of the critical path. There are 4 contributing
factors.
ƒ Duration of each task
ƒ Dependency between tasks
ƒ Allocation of resources
ƒ Task interdependency through the use of common resources
In this tutorial we will develop the critical path based on estimated task duration and task dependencies. We will
assume that the tasks are of fixed duration; therefore the allocation of resources has no effect.
Consider the following tasks:
WBS
Task name
1.1.1
1,1,2
1.2.1
1.2.2
2.1.1
2.1.2
2.2.1
2.2.2
3.1.1
3.1.2
3.2.1
Preparation of Project Plans
Staff Selection
Preparation of Status Reports
Preparation of the PCR
Development of Prototypes
Preparation of artwork
Specification of Architecture
Specification of Functionality
Database Design
Interface Design
HTML Coding
3.2.2
3.2.3
3.3.1
Database Configuration
Development of MIS Reports
Component Testing
3.3.2
System Testing
3.4.1
3.4.2
4.1.1
4.2.1
Vendor Selection
Installation of the equipment
Prepare Documentation
Acceptance
Predecessor
1.1.1
4.2.1
2.1.1
2.1.1
2.2.1
2.2.2
2.2.2
2.1.1
3.1.2
3.1.1
3.1.1
3.2.1
3.2.2
3.2.3
3.3.1
3.4.2
2.2.1
3.4.1
3.1.2
3.3.2
4.1.1
Effort (days)
5
5
1x
4
5
5
10
10
10
5
40
15
10
10
10
3
15
4
1
Create a new Project
Open MS Project and from the File menu select New to create a new project. The following dialogue appears:
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Developing the Critical Path in MS Project
Fig 1
Alternatively from the Project menu select Project Information to see this dialogue for an existing project.
You need to enter the start date, which by default is the current date. The Schedule from option is used to
schedule your project forward form the start date, or backwards from the end date.
Enter Task information
The Gantt view is a convenient place to enter basic task information. Enter the task name and
duration. Start and finish dates will appear automatically, together with duration bars. To add
columns, right-click on the position you want the new column to appear and select the column from
the following menu:
Fig 2
The WBS is defined by the indentation and bolding of Phases and Activities. The duration of an
Activity or a Phase is automatically defined by the individual durations of the tasks underneath.
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Developing the Critical Path in MS Project
Fig 3
Note that task 1.2.1 is a recurring task, as it happens at the beginning of every month. To define a
recurring task select Recurring Task... from the Insert menu. The following dialogue appears:
Fig 4
You can select the frequency of recurrence, the start date and the end date. You can also specify a
calendar to prevent the task recurring on a holiday or a day not available to the project.
Going back to the task definition screen, you can inspect the detailed information for each task by
double-clicking on the task. The following dialogue appears:
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Developing the Critical Path in MS Project
Fig 5
Priority is used to control the scheduling algorithm. A lower number (high priority) task will be
scheduled ahead of a higher number (lower priority) when both tasks are constrained by common
resource(s).
Under the Advance Tab you can define the constraint type and the task type. If the constraint type is
other than As Soon As Possible, the appropriate dare must be entered. You can also specify a deadline
date to alert you of if the task is not finished by that date.
Fig 6
The Task type defines the behaviour during scheduling.
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Developing the Critical Path in MS Project
Fixed Units:
the task requires a fixed number of work units to complete, and adding resources
will shorten the task duration. This is our assumption in this tutorial.
•
If you revise units in a fixed-unit task, Microsoft Project recalculates duration.
•
If you revise duration, Microsoft Project recalculates work.
•
If you revise the amount of work, Microsoft Project recalculates the duration.
Fixed duration: the addition of resources will not have an impact on the duration of the task, but
on the effort spent by each resource.
Fixed Work:
•
If you revise units, Microsoft Project recalculates work.
•
If you revise duration in a fixed-duration task, Microsoft Project recalculates work.
•
If you revise the amount of work, Microsoft Project recalculates the units.
the amount of work remains constant, regardless of any change in duration or resource
assignment units for the task
•
If you revise units, Microsoft Project recalculates duration.
•
If you revise duration, Microsoft Project recalculates units.
• If you revise the amount of work in a fixed-work task, Microsoft Project recalculates
the duration.
The Effort driven option is used to dynamically adjust the task duration each time resources are
allocated or de-allocated to the task.
Enter task dependency
The easiest way to create dependencies is to drag one task onto the other. Alternatively you can
highlight both tasks and click on the link icon
. Note that the sequence in which you drag, or
highlight will determine the direction of the link. As you create the links, the start and finish dates
will be adjusted to reflect the dependencies, and your project will look like this:
Fig 7
To review any particular dependency, you can click on the arrow to display the following dialogue:
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Developing the Critical Path in MS Project
Fig 8
The Type field allows you to change the type of dependency to any of the four dependency types:
ƒ Finish to start
ƒ Finish to finish
ƒ Start to finish
ƒ Start to Start
The Lag field allows you to enter a lag time between activities. This is a better method than creating a
dummy task with no resources.
Viewing the Critical Path
At this point the project finish date has been set according to the duration of the critical path. To
inspect the critical path, any one of a number of views will show it. For example the Network
diagram, or the Tracking Gantt view shows the tasks on the critical path highlighted according to the
option settings. The following is the Tracking Gantt view.
Fig 9
You can change the colour and outline of the chart by selecting the appropriate options in the Format
menu.
© Rob Jeges
www.projectware.com.au
Microsoft Project (MS Project) is a trademark of the Microsoft
Corporation.
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