Project Planning and Scheduling
What this domain tests
This domain tests whether you can build and analyze a schedule model: estimate durations, sequence work, identify the critical path, calculate float, and choose compression techniques. Expect network-diagram and earned-schedule-style questions.
Dependencies and estimating
- Dependencies are mandatory, discretionary, internal, or external. Finish-to-start is most common; start-to-start, finish-to-finish, and start-to-finish also occur.
- Leads allow overlap; lags impose waiting time.
- Analogous estimating uses historical similarity and is fast but less accurate. Parametric uses a statistical relationship. Bottom-up estimates work packages and is more accurate but slower. Three-point estimating uses optimistic, most likely, and pessimistic values; PERT uses (O + 4M + P)/6.
Critical path and float
- The critical path is the longest path through the network, not the shortest.
- Total float is the amount an activity can slip without delaying the project finish; it equals late start minus early start, or late finish minus early finish. Critical activities have zero float in a simple network.
- Free float is the amount an activity can slip without delaying its successor.
- Crashing adds resources or cost to shorten duration. Fast tracking overlaps activities, increasing coordination and rework risk.
- Resource leveling may change the critical path; resource smoothing uses available float without changing it.
Worked example
A start activity feeds B (4 days) and C (5 days); both feed D (2 days); A takes 3 days. Path A-B-D = 3+4+2 = 9 days. Path A-C-D = 3+5+2 = 10 days. The critical path is A-C-D at 10 days. B has total float of 1 day: it can finish one day later without moving D. If B's duration becomes 6 days, both paths take 10 days and the project has two critical paths.
Traps
- Calling the shortest path critical.
- Confusing total float with free float.
- Assuming crashing is always possible or cheap.
- Forgetting that fast tracking raises rework risk.
- Ignoring that resource leveling can create a new critical path.