Project Planning, Scheduling, and Cost Control
What the exam tests
Project planning, scheduling, and cost control tests work breakdown, critical path method, float, and earned value. Expect network logic, float calculations, and interpretation of SPI and CPI.
Core rules and concepts
- A work breakdown structure decomposes scope into manageable packages; each activity needs a duration, logic links, and a resource basis.
- Total float = late start − early start (or late finish − early finish); free float is the delay possible without affecting the next activity.
- The critical path is the longest path through the network and has zero total float; delaying it delays completion.
- Earned value: SPI = EV/PV and CPI = EV/AC. SPI below 1 means behind schedule; CPI below 1 means over budget.
- Estimate at completion (EAC) = BAC/CPI when current cost performance is expected to continue.
- Cash flow follows the S-curve; retentions and payment lags affect the funding requirement.
Worked example
A project has BAC $500,000, PV $200,000, EV $180,000, and AC $210,000. SPI = 180,000/200,000 = 0.90, so the project is behind schedule. CPI = 180,000/210,000 = 0.857, so it is over budget. Forecast EAC = 500,000/0.857 = $583,000. The reasoning uses EV in both numerators; substituting AC into SPI is a common error that gives a meaningless ratio.
Traps that cost marks
- Using AC instead of EV in the SPI formula.
- Confusing total float with free float.
- Identifying the critical path by the most expensive activities rather than the longest path.
- Claiming progress by cost spent rather than work completed.
- Forgetting that float can be consumed by earlier activities.