(04) Leads and Lags Flashcards
What is a Project Network Diagram?
A flow chart that graphically depicts the sequence, interdependencies and start and finish times of the project activities.
What are the benefits of a Project Network Diagram?
- Provides the basis for scheduling labour and equipment.
- Enhances communication among project participants.
- Provides an estimate of the project duration
- Provides a basis for budgeting cash flow.
- Identifies the critical activities.
- Help managers get and stay on plan.
What three questions should be answered for Forward Pass Computation?
- How soon can the activity start?
- (early start – ES). - How soon can the activity finish?
- (early finish – EF). - How soon the project can be finished?
- (expected time –
TE).
What three things should be remembered for Forward Pass Computation?
- Add activity times along each path in the network.
- (ES + duration = EF). - Carry the EF to the next activity, where it becomes ES, unless..
- The successor is a merge activity. If so..
- Select the largest EF of all its immediate predecessors.
What four questions should be answered for Backward Pass Computation?
- How late can the activity start?
- (late start – LS). - How late can the activity finish?
- (late finish – LF). - Which activities represent the critical path (CP)?
- How long can the activity be delayed?
- (slack or float – SL).
What three questions should be remembered for Backward Pass Computation?
- Subtract activity times along each path starting with the project end activity.
- (LF – duration = LS). - Carry the LS to the next predecessor to establish its LF, unless…
- The next predecessor is a burst activity. If so..
- Select the smallest LS of all its immediate successors to establish its LF.
What is Critical Path?
- The series of activities that determine the earliest time by which the project can be completed.
- The longest path through the network diagram and has the least amount of slack (or float).
The path containing the critical task is what is driving the completion date for the project.
The critical path analysis is a network diagramming technique used to predict total project duration.
What are leads and lags?
Values that slightly alter the relationship between two or more work packages.
What is lead time?
- A negative value because time is subtracted from a downstream activity.
What is the extended definition (of lead time)?
This is an overlap between two tasks that are linked by a dependency. For example, if a task can start when its predecessor is half finished, you can establish a finish-to-start dependency and specify a lead time of 50% for the successor task.
- You enter the lead time as a negative value.
What is lag time?
- Minimum amount of time a dependent activity must be delayed to begin or end.
- A positive value because time is added to a downstream activity.
What is the minimum amount of time a dependent activity must be delayed to begin or end?
- Lengthy activities are broken down to reduce the delay in the start of successor activities.
- Lags can be used to constrain finish-to-start, start-to-start, finish-to-finish or start-to-finish or a combination of relationships.
What is the extended definition (of lag time)?
A delay between two tasks that are linked by a dependency. For example, if there must be a two-day delay between the finish of one task and the start of another, you can establish a finish-to-start dependency and specify two days of lag time for the successor task. You enter the lag time as a positive value. Adding lag time is a way to add slack (also called “float” or “buffer”) to a task, increasing the amount of time the task can be delayed before it affects the start of another task.
What is it Laddering?
Breaking activities into segments so the following activity can begin sooner and not delay the work.
