The Critical Path Method


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The Critical Path Method

  1. 1. Critical Path Method Project Management
  2. 2. Critical Path Method • Scheduling and Project Management tool developed in the 1950’s • Allow us to plan all tasks which must be completed in a project • Aids time scheduling and resource planning • They allow progress towards project goals to be tracked
  3. 3. Using the Critical Path Method • Some activities cannot be started until previous activities have been completed • Activities in a critical path method therefore need to be completed in sequence • These activities are known as sequential activities • In addition to these activities there are tasks which can be completed at any time • These activities are known as non-dependent or parallel tasks
  4. 4. Drawing a Critical Path Method Chart Step 1: • List all the tasks needed for the project in the plan • This can be done using a Work Breakdown Structure For each task state: • The earliest start date • The estimated time it will take
  5. 5. Drawing a Critical Path Method Chart Step 2: • Establish whether the activity is sequential or parallel • For sequential tasks dependant tasks should be highlighted Establish sequence by looking at: • Which tasks should take place before this task happens. • Which tasks should be completed at the same time as this task. • Which tasks should happen immediately after this task.
  6. 6. Drawing a Critical Path Method Chart Step 3: • Draw each task as part of a circle and arrow diagram • Each circle or node should show a task within the project and give start and finish times • The circles are numbered to allow them to be easily identifiable • The arrows or arcs which run from circle to circle show the activities needed to complete the tasks • A description of the task should be written under the arrow, with the duration of the task written above it. • Arrows always run left to right
  7. 7. Examples of Critical Path Method
  8. 8. Drawing a Critical Method Chart Step 4: • Identify the critical path • This is done by determining the four parameters of each task in the network • Earliest start time (ES) - The earliest time an activity can start once the previous dependent activities are over. • Earliest finish time (EF) - ES + activity duration. • Latest finish time (LF) - The latest time an activity can finish without delaying the project. • Latest start time (LS) - LF - activity duration. • The float time for an activity is the time between the earliest (ES) and the latest (LS) start time or between the earliest (EF) and latest (LF) finish times. • During the float time, an activity can be delayed without delaying the project finish date. • The activities in the critical path have an effect on the deadline of the project. • If an activity of this path is delayed, the project will be delayed.
  9. 9. Benefits of the Critical Path Method The benefits of CPM are: • Visual representation • The project plan can be tested to ensure it is well thought out • It identifies key tasks which could cause delays to the project if not completed on time • It identifies tasks which could be delayed in order to complete other tasks which are more time crucial • It identifies the minimum amount of time a project will take to complete • It identifies any project steps which can be completed faster in order to complete the project on time
  10. 10. Disadvantages of Critical Path Method The disadvantages of CPM are: • Can be more difficult to understand than Gantt Charts • The time needed for tasks is not as clear as with Gantt Charts
  11. 11. More Information on Critical Path Method • This is a useful video which sums the information given in the slides and will aid understanding of the critical path method
  12. 12. Further Reading • Kelley, J. E. (1963). The critical-path method: Resources planning and scheduling. Industrial scheduling, 347-365. • Leach, L. P. (1999). Critical chain project management improves project performance. Project Management Journal, 30, 39-51. • Maylor, Project Management. Chapter 7
  13. 13. References • Maylor, H., 2010. Project Management. 4th Ed. Chester: Pearson. • MindTools, 2013. Critical Path Analysis and PERT Charts. [Online] Available at: [Accessed on 07/11/13] • Margaret Rouse, 2011. Critical Path Method (CPM). [Online] Available at: [Accessed on 07/11/13] • Tutorialspoint, 2013. Critical Path Method. [Online] Available at: m [Accessed on 07/11/13]