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Dummy activity; use of critical path in CPM

Short answer

A dummy is a zero-duration, zero-resource activity drawn as a dashed arrow to show logical dependence or give unique event numbers. The critical path in CPM gives the minimum project duration, identifies zero-float critical activities needing priority control, guides crashing, and allows float on non-critical activities for resource levelling.

What is a dummy activity? Write down the use of critical path in a CPM network diagram.

Dummy activity

A dummy activity is an activity of zero duration and no resource, drawn as a dashed arrow, used in an arrow diagram to show logical dependence or to give unique event numbers.

Use of critical path in a CPM network

  • Gives the minimum time to complete the project (the length of the longest path).
  • Identifies the critical activities that have no float; they need close control and priority in resources.
  • Shows that a delay of a critical activity delays the whole project, so delay is predicted and corrected early.
  • To shorten the project duration (crashing), only the critical path is shortened.
  • Non-critical activities have float, which is used for resource levelling and flexible scheduling.
  • Helps in cost-time trade-off and in updating the schedule during execution.

✓ Answer checked by Claude Opus 5.5 (high effort)

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