Project Management Critical Path Method 4 — Questions and Answers
Question 1: In which industry was the Critical Path Method (CPM) originally developed in the late 1950s?
- Aerospace and defense
- Construction and chemical manufacturing (Correct answer)
- Information technology
- Healthcare and pharmaceuticals
Correct answer: Construction and chemical manufacturing
CPM was developed jointly by DuPont and Remington Rand in 1957 for managing chemical plant maintenance and construction projects.
Question 2: A project activity has ES=5, EF=12, LS=8, LF=15. What is the activity's total float and duration?
- Float=3, Duration=7 (Correct answer)
- Float=7, Duration=3
- Float=3, Duration=3
- Float=7, Duration=7
Correct answer: Float=3, Duration=7
Duration = EF - ES = 12 - 5 = 7 days; Total Float = LS - ES = 8 - 5 = 3 days (or LF - EF = 15 - 12 = 3 days).
Question 3: When performing schedule compression using 'crashing,' a project manager should first target activities that:
- Have the most remaining duration
- Are on the critical path with the lowest cost slope (cheapest to crash) (Correct answer)
- Have the most total float available
- Involve the most resources
Correct answer: Are on the critical path with the lowest cost slope (cheapest to crash)
Crashing should prioritize critical path activities with the lowest cost-per-unit-of-time-saved (cost slope) to minimize the additional cost of compression.
Question 4: What is the 'near-critical path' in CPM scheduling?
- The path that becomes critical after resource leveling
- A path with very little total float that could easily become critical if delays occur (Correct answer)
- The second-longest path regardless of its float value
- A path containing at least one milestone activity
Correct answer: A path with very little total float that could easily become critical if delays occur
Near-critical paths have minimal total float and pose significant schedule risk because small delays can turn them into the critical path.
Question 5: In CPM, what does it mean when two activities are said to have a 'Finish-to-Finish (FF)' dependency with a lag of 3 days?
- Activity B must start 3 days after Activity A finishes
- Activity B cannot finish until 3 days after Activity A finishes (Correct answer)
- Activity A and B must both finish within 3 days
- Activity B must finish 3 days before Activity A finishes
Correct answer: Activity B cannot finish until 3 days after Activity A finishes
An FF+3 dependency means the successor activity's finish must be at least 3 days after the predecessor's finish.
Question 6: How does adding a project buffer at the end of a Critical Chain Project Management (CCPM) schedule differ from traditional CPM?
- CCPM adds buffers to individual activities; CPM adds one at the end
- CCPM removes safety time from individual tasks and consolidates it into buffers at chain endpoints; CPM uses deterministic single-point estimates throughout (Correct answer)
- CCPM uses resource buffers while CPM uses time buffers
- CCPM ignores the critical path while CPM focuses on it exclusively
Correct answer: CCPM removes safety time from individual tasks and consolidates it into buffers at chain endpoints; CPM uses deterministic single-point estimates throughout
CCPM strips safety time padding from individual tasks, aggregates it into project and feeding buffers, and manages the chain based on resource availability.
Question 7: A project's critical path is A→B→D→F with a total duration of 30 days. Path A→C→E→F has a duration of 27 days. If Activity C is delayed by 4 days, what happens?
- The project is delayed by 4 days
- The project is delayed by 1 day because path A→C→E→F becomes the new critical path at 31 days (Correct answer)
- There is no impact since the path has 3 days of float
- Activity F must be crashed to maintain the original end date
Correct answer: The project is delayed by 1 day because path A→C→E→F becomes the new critical path at 31 days
Path A→C→E→F had 3 days of float; a 4-day delay consumes all float and extends this path to 31 days, making it the new critical path and delaying the project by 1 day.
Project Management Critical Path Method 4
In which industry was the Critical Path Method (CPM) originally developed in the late 1950s?