Project Management Critical Path Method 2 — Questions and Answers
Question 1: In CPM, what does 'free float' (free slack) represent?
- The amount of time an activity can be delayed without delaying the project end date
- The amount of time an activity can be delayed without delaying any successor activity's early start (Correct answer)
- The difference between an activity's late finish and early finish
- The total time available in the project schedule buffer
Correct answer: The amount of time an activity can be delayed without delaying any successor activity's early start
Free float is the amount of time an activity can be delayed without affecting the early start of any immediate successor.
Question 2: A project network has Activity A (3 days) → Activity C (4 days) and Activity B (5 days) → Activity C. What is the earliest Activity C can start if both A and B start on Day 1?
- Day 4
- Day 6 (Correct answer)
- Day 7
- Day 9
Correct answer: Day 6
Activity C can start only after both predecessors finish: A ends Day 4, B ends Day 6, so C starts Day 6 (using 0-based indexing where Day 1 = start).
Question 3: Which scheduling technique uses a single time estimate per activity, unlike PERT which uses three?
- Gantt chart method
- Critical Path Method (CPM) (Correct answer)
- Monte Carlo simulation
- Resource leveling
Correct answer: Critical Path Method (CPM)
CPM uses a single deterministic time estimate per activity, while PERT uses optimistic, most likely, and pessimistic estimates.
Question 4: If the project completion date is moved earlier by management, what is the effect on the critical path?
- The critical path disappears
- Non-critical activities may gain positive float
- Some previously non-critical activities may become critical (Correct answer)
- The critical path always shortens automatically
Correct answer: Some previously non-critical activities may become critical
Compressing the required end date reduces total float across the network, potentially making previously non-critical paths critical.
Question 5: What is 'negative float' in a project schedule?
- Float belonging to activities not on the critical path
- An indicator that the project cannot be completed by the required date without intervention (Correct answer)
- A calculation error in the network diagram
- Float that occurs when resources are over-allocated
Correct answer: An indicator that the project cannot be completed by the required date without intervention
Negative float means an activity's late finish is earlier than its early finish, indicating the schedule is infeasible without corrective action.
Question 6: During a backward pass in CPM, how is the Late Start (LS) of an activity calculated?
- LS = Late Finish + Duration
- LS = Late Finish - Duration (Correct answer)
- LS = Early Start + Total Float
- LS = Early Finish - Duration
Correct answer: LS = Late Finish - Duration
Late Start is calculated as Late Finish minus the activity's duration, working backwards through the network.
Question 7: What scheduling constraint creates a 'Start-to-Finish' (SF) dependency between two activities?
- Activity B cannot start until Activity A finishes
- Activity B cannot finish until Activity A starts (Correct answer)
- Activity A and B must start simultaneously
- Activity A cannot start until Activity B finishes
Correct answer: Activity B cannot finish until Activity A starts
In a Start-to-Finish dependency, the successor (B) cannot finish until the predecessor (A) has started — the rarest of the four dependency types.
Project Management Critical Path Method 2
In CPM, what does 'free float' (free slack) represent?