14. Limitations of PERT

PERT extends the standard CPA but has some advantages

  • The time estimates for optimistic, likely and pessimistic completion is subjective, so an inexperienced planner is less likely to get it right
  • The formula is called a 'beta distribution' but it is by no means certain that this is correct for each activity in a specific project
  • It tends to underestimate project completion time, especially if delays cause the critical path to shift around.

To overcome the last point, if the PERT is modelled on a computer, then a technique called 'Monte Carlo' simulation can be used. This is where each path is allowed to vary randomly slightly (within limits) to see how sensitive the overall project becomes to delays. If a path is partcularily sensitive then management time and resources can be applied to make sure that activity keeps on track.

 

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Click on this link: What is PERT planning