CST CPM & PERT Schedule Development 3 — Questions and Answers
Question 1: When converting an Arrow Diagramming Method (ADM) network to a Precedence Diagramming Method (PDM) network, dummy activities are:
- Converted to SS relationships with zero lag
- Eliminated because PDM uses node-based logic to capture dependencies directly (Correct answer)
- Converted to mandatory milestones in PDM
- Retained as zero-duration activities to preserve logic
Correct answer: Eliminated because PDM uses node-based logic to capture dependencies directly
PDM places activities on nodes and uses dependency arrows with relationship types, making ADM's dummy activities unnecessary.
Question 2: A project manager wants to compress the schedule by overlapping phases. Which CPM technique involves starting a successor activity before its predecessor is fully complete?
- Crashing
- Resource leveling
- Fast-tracking (Correct answer)
- Monte Carlo simulation
Correct answer: Fast-tracking
Fast-tracking overlaps activities that would normally be done sequentially, introducing parallel work and potential rework risk.
Question 3: In PERT, if the optimistic estimate is 6 days, pessimistic is 18 days, and most likely is 9 days, what is the PERT expected duration?
- 9 days
- 10 days (Correct answer)
- 11 days
- 12 days
Correct answer: 10 days
PERT expected duration = (6 + 4×9 + 18) / 6 = (6 + 36 + 18) / 6 = 60 / 6 = 10 days.
Question 4: Which statement about the Critical Path Method is TRUE regarding resource constraints?
- CPM inherently accounts for resource availability when calculating float
- CPM assumes unlimited resources and does not factor resource constraints into float calculations (Correct answer)
- CPM requires resource leveling to be performed before calculating the critical path
- CPM and resource leveling always produce the same critical path
Correct answer: CPM assumes unlimited resources and does not factor resource constraints into float calculations
Traditional CPM is a pure logic-based technique that assumes resources are always available; resource constraints are handled separately through leveling.
Question 5: A 'near-critical path' in a CPM network is significant because:
- It always has negative float and requires immediate corrective action
- It may become critical if activities on it experience delays, creating schedule risk (Correct answer)
- It represents the shortest possible project duration
- It is used only in PERT analysis, not in CPM
Correct answer: It may become critical if activities on it experience delays, creating schedule risk
Near-critical paths with small total float are vulnerable to becoming critical if minor delays occur, representing a key schedule risk.
Question 6: When 'crashing' a schedule in CPM, a scheduler should prioritize crashing activities that:
- Have the most total float
- Are on the critical path and have the lowest cost-slope (Correct answer)
- Are on near-critical paths with the highest risk
- Have the longest duration regardless of path
Correct answer: Are on the critical path and have the lowest cost-slope
Crashing the critical path activity with the lowest cost per day saved maximizes schedule compression per dollar spent.
Question 7: In CPM network analysis, an 'open end' in the schedule logic (an activity with no successor other than the project end) is problematic because:
- It creates a second critical path automatically
- It may mask float and make the schedule difficult to control and analyze (Correct answer)
- It is required by AACE standards for all summary activities
- It reduces the total number of paths in the network
Correct answer: It may mask float and make the schedule difficult to control and analyze
Open ends create dangling logic that can artificially inflate or hide float, making the schedule unreliable for analysis.
CST CPM & PERT Schedule Development 3
When converting an Arrow Diagramming Method (ADM) network to a Precedence Diagramming Method (PDM) network, dummy activities are: