Critical path method


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Critical path method

  1. 1. Critical Path Method
  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 need to be completed in sequence ▪ These activities are known as sequential activities ▪ In addition to these, other tasks can be completed at any time ▪ These activities are known as non-dependent or parallel tasks
  4. 4. Drawing a CPM Chart: Step 1 • 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 CPM Chart: Step 2 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 CPM Chart: Step 3 ▪ Each circle/node should show a task within the project; ▪ Each circle/node should give start and finish times; ▪ Each circle/node should be numbered; ▪ The arrows/arcs should the sequence of the tasks; ▪ A description and duration of the task should be written under the arrows; ▪ Arrows should always run left to right
  7. 7. Examples of Critical Path Method
  8. 8. Drawing a CPM Chart: Step 4 ▪ Determining the four parameters of each task in the network 1. 2. 3. 4. 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 ▪ 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 ▪ 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: tm [Accessed on 07/11/13]