Chapter 5 Developing the Schedule

Estimate Activity Resources

Resources include

People, materials, equipment, facilities

Influence on the duration（important）

Availability of the resources

Types of resources

Sufficient quantities of resources for the activity durations

Potential conflicts with other projects may cause

Involve person with expertise in resource estimate

Estimates influence costs

【•It is necessary to estimate the types and quantities of resources that will be required to perform each specific activity in a project.

•Resources include people, materials, equipment, facilities, and so forth.

•Having this information is essential in estimating how long it will take to perform each activity and the project as a whole.

•A number of factors influence the duration of an activity:

•Availability of the resources

•Types of resources

•Sufficient quantities of resources for the durations of the activities

•Potential conflicts with other projects that may cause a delay

•When estimating the types and quantities of resources required for each specific activity, it is valuable to involve a person who has expertise or experience with the activity.

•Estimated activity resources will also be used later for estimating activity costs and determining the project budget.】

Estimate Activity Durations

Duration must be the total elapsed time

Time for the work to be done plus any associated waiting time

Builds buy-in from the person and generates commitments

Avoids bias that may be introduced by having one person estimate the durations for all of the activities

The designated individual uses experience to estimate the durations

Historical data can be used as a guide

The estimated duration should be aggressive yet realistic.

Durations should not be too short to try to win the contract

Inflated estimated durations is not good practice

Project manager may not be able to negotiate shorter durations

Some activities will take longer and others shorter durations than planned

As the project progresses, level of confidence for accuracy increases

【•Once the types and quantities of resources are estimated for each activity, estimates can be made for how long it will take to perform the activities.

•The estimated duration for each activity must be the total elapsed time—the time for the work to be done plus any associated waiting time.

•The figure above depicts the activity estimated duration for varnishing floors.

•It is a good practice to have the person who will be responsible for performing a specific activity estimate the duration for that activity.

•Builds buy-in from the person and generates commitments

•Avoids bias that may be introduced by having one person estimate the durations for all of the activities

•It is important to designate an experienced individual to estimate the durations for all the activities for which the organization or subcontractor is responsible in large projects.

•Historical data can be used as a guide in estimating the durations of similar activities.

•Estimated duration should be aggressive yet realistic.

•Inflating estimated durations in anticipation of the project manager negotiating shorter durations is not a good practice.

•Throughout the performance of the project, some activities will take longer than their estimated duration, others will take less time than estimated, and a very few may conform to the estimated duration exactly.

•At the beginning of the project, it may not be possible to estimate the durations for all activities with a high level of confidence.

The project team can progressively elaborate the estimated durations as more information is becomes available to allow for more accurate estimated durations.】

Establish Project Start and Finish Times

Define the overall window for project completion

May not want to commit to a specific date

Project not start until customer has approved the contract

Delay in contract signing may impact project start

Set finish time as number of days from project start

【It is necessary to select an estimated start time and a required completion time for the overall project. This is important in order to establish a basis from which to calculate a schedule using the estimated durations for the activities.

•Define the overall window, or envelope, of time in which the project must be completed.

•The contractor may not want to commit to completing the project by a specific date until the customer has approved the contract.

•A delay in signing will likely impact the start date of the project.

•The finish time should be stated as a number of days from the start of the project.】

Total Slack

Sometimes called float

The difference between EF time of last activity and the project required completion time

Negative slack （almost late）

Lack of slack over the entire project

Amount of time an activity must be accelerated

Positive slack （got plenty of time）

Maximum amount of time that the activities on a particular path can be delayed without jeopardizing on-time completion

【•Total slack is sometimes called float.

•It is the difference between EF time of last activity and the project required completion time.

•Total slack is calculated for each of the activities by finding the difference between the EF time of the activity and the LF of the activity.

•You also look at the difference between the ES and LS of the activity.

•Negative slack indicates:

•A lack of slack over the entire project

•The amount of time an activity must be accelerated to complete the project by the required completion time

•Positive slack indicates the maximum amount of time that the activities on a particular path can be delayed without jeopardizing completion of the project by the required completion time.

•If the total slack is zero, the activities on the path do not need to be accelerated, but cannot be delayed.】

Critical Path （what must be accomplished）

Longest path in the overall network diagram

Find which activities have the least amount of slack

【•The critical path is this longest path in the overall network diagram.
•One way to determine which activities make up the critical path is to find which ones have the least amount of slack.】

Incorporate Changes into Schedule

Changes may impact the schedule

Initiated by customer or project team

Result from

Early change may have less impact than later change

Manage requested changes

Estimate impact

Obtain customer approval

Revise project plan, schedule, and costs

【Throughout a project, changes may occur that impact the schedule.

•Changes might be initiated by the customer or the project team, or they might be the result of an unanticipated occurrence.

•Changes requested early in the project may have less of an impact on schedule and budget than those requested later in the project.

•When the customer requests a change, the contractor or project team should estimate the impact on the project schedule and budget and then obtain customer approval before proceeding.

•If the customer approves the proposed revisions to the project schedule and budget, then any additional activities, revised estimated durations, and revised estimated resources and associated costs should be incorporated into the project schedule and budget.

•With respect to the project schedule, changes can result in the addition or deletion of activities, re-sequencing of activities, changes to estimated durations for specific activities, or a new required completion time for the project.】