3.3.4 critical path analysis Flashcards
Critical path analysis is
a technique used to identify the order in which all activities need to be completed when planning a complex project.
Critical path diagrams organise the activities in an order to show which activities can be done simultaneously and which are dependent upon earlier activities.
This allows for the identification of the shortest time in which a project can be completed.
The critical path is
the set of activities that will lengthen the duration of the project if delayed.
Each node is split into 3 parts which are
the left half of the circle -The node number, based upon the order in which it is drawn
top right quarter-The earliest start time (EST) - the earliest the following activity can possibly start
bottom right quarter- The latest finish time (LFT) – the latest an activity can finish without delaying the whole project.
Each activity is shown on a line that connects the nodes, what does the number mean on it
The activity duration is shown below the line
eg 4 weeks
how to complete a Critical path diagram
-Node 1 always starts at 0
-EST is calculated from left to right by adding the duration of the activity to the previous EST
Each line represents an activity
ESTs are calculated from left to right by adding the duration to the previous EST
If more than one activity precedes a node the highest figure becomes the EST
LFTs are calculated from right to left by subtracting the duration from the previous LFT
If more than one activity precedes a node the lowest figure becomes the LFT
The first node will always have an EST and LFT of zero
The final node will always have an EST and LFT that is the same figure
A node preceding an activity that is on the critical path will always have an EST and LFT that is the same
The critical path are those activities that must be completed on time if the whole activity is not to be delayed. These are identified by putting a line through the activity.
what is float time
Non-critical activities are those which are not on the critical path
There is some leeway (spare time) to complete the activities
formula for float time is
LFT – duration – EST
Limitations of using critical path analysis
Is only a starting point for a successful project
Can not stop unexpected delays from happening
Relies on estimations of the duration of each activity
Does not take into account external influences
May encourage inefficient behaviour on non critical activities
Large projects can be too complex for CPA
