Equipment Project Schedule and Cost Control
Domain 7 - Equipment Project Schedule and Cost Control
This domain tests quantitative control: network logic, float, earned value, and the discipline of measuring performance against a baseline rather than against an impression.
Core rules
- WBS and schedule. Break work into work packages; milestone schedules for the client, bar charts for communication, network diagrams (双代号/单代号) for logic. The critical path is the longest path; its activities have zero total float when planned duration equals calculated duration.
- Float. 总时差 (total float) = LS − ES = LF − EF; 自由时差 (free float) = earliest start of successors − EF. Delay within total float does not extend the project; delay consuming free float affects the immediate successor.
- Earned value. PV (BCWS), EV (BCWP), AC (ACWP). CV = EV − AC; SV = EV − PV; CPI = EV/AC; SPI = EV/PV; EAC = BAC/CPI when the variance is typical, or AC + (BAC − EV) when it is atypical.
- Change and claim control. Assess every change for scope, schedule and cost impact before approval; a delay claim needs notice within the contractual time bar, contemporaneous records, proof the event was not the claimant's fault, and proof it affected the critical path.
- Cost control. Estimate → budget → commitment → actual → forecast; S-curve for cash flow and progress comparison; retention and payment certification.
Worked example
At month 6: BAC = 2,000, PV = 800, EV = 720, AC = 780. Then CV = 720 − 780 = −60 (over budget); SV = 720 − 800 = −80 (behind schedule); CPI = 0.923; SPI = 0.90; EAC = 2,000/0.923 = 2,167. Interpretation: cost and schedule are both adverse and linked - the delay consumes supervision and site overhead. The forecast is a 167 overrun at completion if current efficiency persists. The response is to identify which work packages drive the negative SPI, then decide whether resequencing can recover time without compressing every activity.
Traps that cost marks
- Inverting CPI and SPI, or misreading the sign of CV and SV.
- Using EAC = AC + (BAC − EV) when the variance is clearly typical and continuing.
- Treating any delay on a non-critical activity as a schedule claim.
- Reporting percentage complete from cost spent rather than verified physical progress.