Project Management Critical Path Method 5 — Questions and Answers
Question 1: What is the primary purpose of performing a 'forward pass' and 'backward pass' in CPM network analysis?
- To calculate the cost of each activity in both directions
- To determine the early and late start/finish dates and calculate float for each activity (Correct answer)
- To identify resource requirements during project execution
- To validate that the network diagram has no circular dependencies
Correct answer: To determine the early and late start/finish dates and calculate float for each activity
The forward pass calculates early start and early finish dates; the backward pass calculates late start and late finish dates, together revealing float for each activity.
Question 2: A project network diagram contains a loop (circular dependency). What is the standard resolution approach?
- Use the longest path through the loop as the critical path
- Identify and eliminate the incorrect dependency that creates the loop before proceeding with CPM calculations (Correct answer)
- Apply dummy activities to break the loop
- Use Monte Carlo simulation to model the loop's uncertainty
Correct answer: Identify and eliminate the incorrect dependency that creates the loop before proceeding with CPM calculations
Loops (circular logic) make CPM calculations impossible; the incorrect dependency relationship must be identified and corrected in the network diagram.
Question 3: In a Precedence Diagramming Method (PDM) network, what does a 'Start-to-Start (SS) with lag of 5' relationship mean?
- Both activities must start at the same time, with 5 days allocated between them
- The successor activity cannot start until 5 days after the predecessor activity starts (Correct answer)
- The successor activity must start exactly 5 days before the predecessor finishes
- Both activities must finish within 5 days of each other starting
Correct answer: The successor activity cannot start until 5 days after the predecessor activity starts
SS+5 means the successor cannot begin until at least 5 days have elapsed since the predecessor started, allowing some overlap while enforcing a minimum lead time.
Question 4: Which of the following scenarios would most likely cause the critical path to CHANGE during project execution?
- A critical path activity finishes exactly on schedule
- A non-critical activity experiences a delay greater than its total float (Correct answer)
- The project sponsor approves additional budget for the project
- A non-critical activity finishes 2 days early, while its total float was 5 days
Correct answer: A non-critical activity experiences a delay greater than its total float
When a non-critical activity's delay exceeds its total float, it exhausts all schedule flexibility and its path becomes the new (or parallel) critical path.
Question 5: What distinguishes 'interfering float' from 'independent float' in CPM?
- Interfering float can be used without affecting the project end date; independent float cannot
- Independent float can be used without affecting any predecessor or successor's schedule; interfering float affects either predecessors or successors if used (Correct answer)
- Interfering float applies only to the critical path; independent float applies to non-critical activities
- Independent float is calculated in the forward pass; interfering float in the backward pass
Correct answer: Independent float can be used without affecting any predecessor or successor's schedule; interfering float affects either predecessors or successors if used
Independent float is the safest type — using it affects neither predecessors' late dates nor successors' early dates; interfering float, if used, may impact adjacent activities.
Question 6: A project manager is reviewing a schedule and finds that the critical path runs through a single vendor's deliverable. What is the best risk response?
- Re-sequence all activities to remove the vendor from the critical path immediately
- Identify and accelerate a near-critical parallel path, monitor the vendor closely, and develop contingency plans (Correct answer)
- Add a 50% duration buffer to the vendor activity
- Replace the vendor with an internal resource to eliminate the risk
Correct answer: Identify and accelerate a near-critical parallel path, monitor the vendor closely, and develop contingency plans
The best response combines proactive monitoring, near-critical path management, and contingency planning rather than an immediate disruptive change to the network.
Question 7: When using CPM for a complex project, how should a project manager treat 'hammock activities'?
- As critical path activities that must be crashed first during compression
- As summary activities that span from the start of the first sub-activity to the end of the last, with duration determined by those sub-activities (Correct answer)
- As activities with zero float that represent project milestones
- As parallel activities that can be fast-tracked without risk
Correct answer: As summary activities that span from the start of the first sub-activity to the end of the last, with duration determined by those sub-activities
Hammock (or span) activities are summary bars whose start and finish are tied to the actual activities they encompass, making their duration dependent on the underlying work.
Project Management Critical Path Method 5
What is the primary purpose of performing a 'forward pass' and 'backward pass' in CPM network analysis?