D1 - Critical Path Analysis Flashcards
How do you provide a visual representation of the information given in a precedence table?
Create an activity network.
What is a precedence/dependence table?
How activities are shown that can only be started once others are completed.
What is the completion I an activity?
An event.
Describe how you create an activity on arc network.
The activities are arcs.
The events are nodes.
The nodes are numbered from 0, this is the source node.
The final node is the sink node.
Describe dummy activities.
Shown by a dotted line, it has no time or cost involved.
Can only be one activity between two events.
What is the early event time?
The earliest time of arrival at the event allowing for the completion of all preceding activities.
What is the late event time?
Is the latest time that the event can be left without extending the time needed for the project.
How are early event times calculated?
Using a forward pass.
Start at the source node and work out all routes to the sink node.
The largest route is the early event time.
How do you calculate the late event time?
Backward pass.
Make the early event time the late event time at the sink node.
Work backwards and always use the smallest route possible at each node.
What is a critical activity?
An activity where an increase in it’s duration results in a corresponding increase in the duration of the whole project.
(All the nodes in a critical path)
The early and late event time will be equal on critical activities.
What is a critical path?
The longest path contained in the network.
Consists of critical activities.
What is the total float?
Latest finish time - duration - earliest start time.
The amount of time that it’s start may be delayed without affecting the duration of the project.
Any delay in a critical activity will affect the project. Total Float = 0
What provides a graphical way to represent the range of possible start and finish times for all activities on a single diagram?
A cascade (Gantt) chart.
What is a scheduling program used for?
To show how tasks are allocated to workers in order to complete a project subject to constraints on the time required or the number of workers available.
How do you work out the lower bound for the number of workers needed?
Sum of all activity times/critical time of the project.
