Direct answer
Calculate cost and schedule performance indexes from earned value data, then interpret efficiency without confusing value-based schedule results with time.
What to know
- Use consistent units for all inputs.
- Validate zero and negative values before dividing.
- State the forecasting assumption before using an output for a decision.
- Reconcile calculator results with the approved project data date and baseline.
How to apply it
Enter current, controlled project data. Review the formula and model limits before communicating the result, and retain the input values with the analysis.
Formula
CPI = EV ÷ AC; SPI = EV ÷ PV.
Worked example
If EV is 80, AC is 100, and PV is 90, CPI is 0.80 and SPI is 0.889. The project earned 0.80 units of value per cost unit and completed less value than planned.
Common mistakes
- Mixing currencies or data dates.
- Reporting excessive decimal precision.
- Treating one formula as a guaranteed forecast.
Exam and practice connection
PMP questions can test both calculation and interpretation. Read the wording and identify the requested metric before calculating.