1. Importance of Project Schedules
Managers often cite delivering projects on time as one of their biggest challenges.
Managers also cite schedule issues as the main reason for conflicts on projects throughout the project life cycle.
Time is the one variable that has the least amount of flexibility.
Time passes no matter what happens on a project.
Project time management involves the processes required to ensure timely completion of a project.
Most managers have not used several of the tools and techniques unique to project time management, such as Gantt charts, network diagrams, and critical path analysis.
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2. Processes of Project Time Management
Activity definition: identifying the specific activities that the project team members and stakeholders must perform to produce the project deliverables
Activity sequencing: identifying and documenting the relationships between project activities
Activity duration estimating: estimating the number of work periods that are needed to complete individual activities
Schedule development: analyzing activity sequences, activity duration estimates, and resource requirements to create the project schedule
Schedule control: controlling and managing changes to the project schedule
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3. Project Time Management
Activity Definition
An activity or task is an element of work normally found on the work breakdown structure (WBS) that has an expected duration, a cost, and resource requirements.
Activity definition usually results in the project team developing a more detailed WBS and supporting explanations.
The goal of this process is to ensure that the project team has complete understanding of all the work they must do as part of the project scope.
Activity definition also results in supporting detail to document important product information as well as assumptions and constraints related to specific activities.
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4. Project Time Management
Activity Sequencing
Activity sequencing involves reviewing the activities in the detailed WBS, product descriptions, assumptions, and constraints to determine the relationships between activities.
It also involves evaluating the reasons for dependencies and the different types of dependencies.
A dependency or relationship shows the sequencing of project activities or tasks.
After you define the sequence of activities, you can use some of the most powerful schedule tools available to project managers:
Network diagrams
Critical path analysis
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5. Project Time Management
Types of Dependencies
Mandatory dependencies: (For example, you cannot test code until after the code is written.)
Are inherent in the nature of the work being done on a project.
Cannot be separated from the work.
Discretionary dependencies:
Are defined by the project team and may limit later scheduling options.
Are not controlled by strict rules, but left for the project team to make a decision about in each particular situation.
External dependencies: relationships between project and non-project activities. For example, the installation of new software may depend on delivery of new hardware from an external supplier.
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6. Project Time Management
Network Diagrams
A project network diagram is a basic display of the logical relationships among, or sequencing of, project activities.
The network diagram represents activities that must be done to complete the project.
Some items that the team knows must be done and will be done regardless of other activities do not need to be included in the network diagram.
There are two main diagramming methods:
Activity-on-arrow (AOA) or arrow diagramming method (ADM)
Activity-on-node (AON) or precedence diagramming method (PDM)
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7. Activity-on-arrow (AOA)
This method is a network diagramming technique in which activities are represented by arrows and connected at points called nodes to illustrate the sequence of activities.
AOA network diagrams are generally easy to understand and create.
A node is simply the starting and ending point of an activity.
The first node signifies the start of a project, and the last node represents the end of a project.
Dummy activities (represented with dashed arrow lines) have no duration and no resources but are occasionally needed on AOA network diagrams to show logical relationships between activities.
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8. Activity-on-arrow (AOA)
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9. Activity-on-node (AON)
This method is a network diagramming technique in which boxes (or nodes) represent activities.
The activities are placed inside boxes, which represent the nodes on the diagram.
Arrows and arrowheads show the relationships between activities.
This technique is used more often and has more advantages than the AOA technique:
Most project management software uses this method.
The method avoids the need to use dummy activities.
The method shows different dependencies among tasks, whereas AOA network diagrams use only finish-to-start relationship.
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10. Activity-on-node (AON)
The four types of relationships between activities in the AON method include:
Finish-to-start (wholly used by AOA): a relationship where the “from” activity must finish before the “to” activity can start (the most common type of relationship)
Start-to-start: a relationship in which the “from” activity cannot start until the “to” activity is started
Finish-to-finish: a relationship where the “from” activity must be finished before the “to” activity can be finished although the two activities can be performed at the same time
Start-to-finish (rarely used method): a relationship where the “from” activity must start before the “to” activity can be finished
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11. Activity-on-node (AON)
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12. Activity Duration Estimating
Project team members must document their assumptions when creating duration estimates and update the estimates as the project progresses.
If changes are made to the scope of the project, the duration estimates should be updated to reflect those changes.
It is also helpful to review similar projects and seek the advice of experts in estimating activity durations.
It is also important to review constraints and assumptions related to the estimates.
In addition to reviewing past project information, the team should also review the accuracy of the duration estimates thus far on the project.
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13. Project Time Management
Schedule Development
The ultimate goal of schedule development is to create a realistic project schedule that provides a basis for monitoring project progress for the time dimension of the project.
Several tools and techniques assist in the schedule development process:
A Gantt chart is a common tool for displaying project schedule information.
Critical path analysis is a very important tool for developing and controlling project schedules.
PERT analysis is a means for evaluating schedule risk on projects.
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14. Project Time Management
Gantt Charts
Gantt charts provide a standard format for displaying project schedule information by listing project activities and their corresponding start and finish dates in a calendar format.
The different symbols on a Gantt chart are:
The black diamond symbol represents a milestone – a significant event on a project with zero duration.
The thick black bars with arrows at the beginning and end represent summary tasks.
The light gray horizontal bars represent the duration of each individual task.
Arrows connecting these symbols show relationships or dependencies between tasks.
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15. Project Time Management
Gantt Charts
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16. Project Time Management
Gantt Charts
A tracking Gantt chart is a Gantt chart that compares planned and actual project schedule information including the planned schedule dates for activities or the baseline dates.
Gantt charts have both:
Advantages:
Providing a standard format for displaying planned and actual project schedule information
Being easy to create and understand
Disadvantages:
Usually not showing relationships or dependencies between tasks; or
Not displaying the dependencies as clearly as a network diagram does
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17. Critical Path Analysis
Critical path method (CPM) is a project network analysis technique used to predict total project duration.
A critical path for a project:
Is the series of activities that determine the earliest time by which the project can be completed.
Is the longest path through the network diagram.
Has the least amount of slack or float – the amount of time an activity may be delayed without delaying a succeeding activity or the project finish date.
Crashing – a technique for making cost and schedule trade-offs to obtain the greatest amount of schedule compression for the least incremental cost
Advantage: shortening the time it takes to finish a project
Disadvantage: often increasing total project costs
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18. Project Time Management
PERT Analysis
Program evaluation and review technique (PERT) is a network analysis technique used to estimate project duration when there is a high degree of uncertainty about the individual activity duration estimates.
PERT applies the critical path method to a weighted average duration estimate.
PERT uses probabilistic time estimates instead of one specific or separate duration estimate.
Probabilistic time estimates are duration estimates based on using optimistic, most likely, and pessimistic estimates of activity durations.
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19. Project Time Management
PERT Analysis
To use PERT, you calculate a weighted average for the duration estimate of each project activity using the following formula:
PERT weighted average
= [optimistic time + (4 x most likely time) + pessimistic time]/6
PERT has both:
Advantage: addressing the risk associated with duration estimates
Disadvantages:
Involving more work since it requires several duration estimates
Not as good as some other probabilistic methods for assessing risk
Being confused with network diagrams by many people
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20. Project Time Management
Schedule Control
To control changes to project schedules, project managers have to:
Ensure that the project schedule is realistic
Use discipline and leadership to emphasize the importance of following and meeting project schedules
Manage several people-related issues to keep projects on track including:
Empowerment – empowering project team members to take responsibility for their activities
Incentives – using financial or other incentives to encourage people to meet schedule expectations
Discipline – using discipline to control project schedules
Negotiation – practicing good negotiation skills
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