Schedule Monitoring and Controlling
Status, measure, forecast, act
The control cycle starts at a status date: capture actual start/finish dates, actual durations, remaining durations, and resource usage, then re-run the network. Measure progress consistently (duration-based, units-based, or earned-value-based percent complete) and state which you used. Compare against the approved baseline using variance analysis, float consumption, and critical-path change tracking. Compress with crashing or fast tracking only when analysis supports it. Distinguish a schedule update (data changes within the baseline) from a revision (baseline change requiring approved change control).
Earned value and earned schedule
SV = EV − PV; SPI = EV / PV; CV = EV − AC; CPI = EV / AC. Because SPI converges toward 1.0 as a project nears completion, PMI-SP expects awareness of earned schedule: convert EV to the time at which that PV was planned (ES), then SV(t) = ES − AT and SPI(t) = ES / AT.
Worked example
At month 5, PV = 100, EV = 90. SV = −10 and SPI = 0.90 (behind). Planned cumulative PV reached 90 at month 4, so ES = 4, SV(t) = 4 − 5 = −1 month, and SPI(t) = 0.80. Earned schedule shows a larger delay than SPI alone suggests.
Traps
- Reading SPI > 1 as behind schedule.
- Treating a baseline change as a routine update.
- Recalculating the critical path from the baseline instead of the current update.
- Comparing percent complete figures computed by different methods.
- Ignoring float erosion on near-critical paths before it becomes a delay.