Progress curve - Early Vs Late and somewhere in between

Dear Masood:

there is a extense literature about to S-curves that you can easily find in the web.

I recommend you -among other documents and papers- the Recommended Practice 55R-09 of the AACE (PMI is another good source).

regards 

Thanks Renzo.  I'll check them out. I'm A AACE member actually, and planned to go there as well, but thought to see if any member here practicxally using it!  We are brainstorming using curves other than the early curve at work.  I have used a 50% curve before at different places.  Trying to find out how widespread this is and justify to use.  We are a Petrochemical Company exercising small expansion, revamp, and debottleneck projects ranging from 25 to $400M, having EPCM companies do them for us. Thanks again.     

used all types - ES=0%, ES=50%, ES=67%, ES=100%=LS. seems to be at the PM's whim but earliest and latest seem wrong (never achieve ES and LS gives you no time to correct). trouble with AACE RP's is (unless your a member) they cost $60.

 BUT

make sure that the planned v earned v actual data is consistent (no actual for unbudgetted work, no earned for actuals etc)

that you highlight the function your are measuring e.g. budget, commitment, manhours, quantities, benefit etc

other than ES and LS you don't have a schedule to support the indices so further detailed analysis is not possible

ALSO

say which baseline you are using b0 - original, b1 updated etc. Nothing worse that having to report negative percentage progress cause you have accepted scope changes that increase contract value

ADD

when the indices was produced (as a superscript) e.g. P6 of 28, or M5 of 35 - helps in trending

which planned curve was used (as a subscript) e.g. ES=50%

                                                                 P6 of 36

so SPI = 0.8 becomes  SPI (budget, b0) = 0.8 

                                                                 ES=50%

I have written a paper with full details if you are interested further

Peter