Lessons · Project management · reading a status from the indexes
Reading the status from two numbers
CPI and SPI together give one of four stories: both above 1.0 is ahead and under, both below is late and over, and the mixed cases each have a usual cause worth checking.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
Two indexes on a slide, and the director asks what they mean. She does not want the formulas; she wants the sentence. Under and ahead? Over and behind? Under but behind, which usually means the work is not being done? The reading is the skill.
How to think about it
Read CPI first (money), then SPI (pace), then ask why the pair looks like that. CPI high, SPI low: probably under-staffed, so the work is cheap and slow. CPI low, SPI high: probably paying overtime to hold the date.
Worked example
CPI 1.10, SPI 1.10Ahead of schedule, under cost. Check that EV is measured honestly before celebrating.
CPI 0.80, SPI 0.80Behind and over. The usual state of a project in trouble.
CPI 1.20, SPI 0.90Cheap but slow. Likely a team that is too small: each dollar buys a lot, but not enough dollars are being spent.
CPI 0.85, SPI 1.05Fast but expensive. Likely overtime or extra contractors holding the date.
Your turn
CPI is 0.90 and SPI is 1.10. Write the reading.
Over cost and of schedule; look for overtime.
Solve one, graded on the server
The trap
Reading SPI late in a project. SPI drifts back to 1.0 as EV approaches PV near the end, so a project that is months late can show SPI 0.98 in its final weeks. Near the end, read the schedule from the network, not from SPI.