Sigmoid Curve

Please, be reminded that without the Early and Late curves for the "Work as Projected" the comparison of actuals is not good enough for an estimate of what the CPM model might project.







The same applies to Earned Value, performance compared only to early dates is unfair and is wrong.



https://www.apm.org.uk/download.asp?fileID=198



Traditional schedule EVM metrics are good at beginning of project

••Show schedule performance trends

But the metrics don’t reflect real schedule performance at end

••Eventually, all “budget” will be earned as the work is completed, no matter how late you finish

••••SPI improves and ends up at 1.00 at end of project

••••SV improves and ends up at $0 variance at end of project

••Traditional schedule metrics lose their predictive ability over the last third of project.

Hi Trevor



If it is the case that the Contractor has submitted a forecast payment schedule in the form of an S curve generated from a spreadsheet and not the programme - with no verifiable back up data - then the appropriate response will be to shred it and ask for a proper substantiated document.



Surely there must be more to it than that?



Best regards



Mike Testro

Mike,

the way I am reading it is that Wilfredo is on the client side and has received from the contractor a thing purporting to be an S curve, either cumulative Work in hours or cumulative price (what the client pays the contractor) in $.

Wilfredo has not received enough information to know how the contractor has generated the curve. He hopes that the curve has been generated from the price associated with each task in the program/schedule/Gantt Chart but suspects that it hasn’t been, and if this is the case how reliable it is.

Hi All



I seem to be missing a thing or two in this discussion.



From what I can see someone has prepared a document and is requiring someone else to abide by it.



May I ask:



1. What is the contractual relationship between the parties.

2. Is the document a "contractual" document.

3. What are the penalties - if any - of not complying with the request.



Best regards



Mike Testro

Wilfredo, If they can show you the curve then they can show you the data that they used to generate it. One without the other is only half the picture.

The program has to come into it somewhere, one would think.

Normally, the price of each task would accrue pro-rata, but it would be ok to attach the price of each task to the start date of each task and make the S curve from that.

You would just need a list of dates and amounts.

But I suspect that they have not even done that.

If so, and they have just assumed an S shaped curve, then, well, this just sucks.

Dear Wilfredo,



The scheduling tools and excel both use data to generate the S-curves. You need to understand the building blocks of the S-curve and then you can determine if the data that they have submitted is correct or not. You can do the S-curve by hand as well.



Try to understand the sequence of what they have done and if that is acceptable to you or not. Then you can do the number crunshing and determine if the numbers are correct or not.



With kind regards,



Samer

Wilfredo, this is how I understand your description of what has occurred.



The contractor has provided a "schedule" or "program" in the form of a list of tasks, durations and a predecessor network resulting in, and presented as, a Gantt Chart. This "program" has not asigned resources or costs (or price) to the tasks. Therefore, it is not possible to use the "program" to generate directly the cumulative price curve, which we would normally expect to be approximately S shaped.



The contractor has also provided an S shaped curve which purports to be a cumulative price curve. I do not know, from your description, whether the contractor has derived the dates and cumulative amounts for the curve from the "program", but if there is no price data in it then it is unlikely. It is possible to get the data to generate the cumulative price curve from the "program" without price loading the tasks in the "program", but this would be doing it the hard way. It is possible that the contractor has ignored the "program" and just assumed an S shaped curve which accumulates to the total price, and then worked backwards to extract the data from the curve to attach price amounts to dates.



I have some ideas about whether this is good or bad, but first, is this correct?

Dear Wilfredo,



Unless the tool is specified in the Conditions of Contract, it does not matter what the Contractor submit as long as it is logical and represent the sequence of events that is going to take place.



You can revert to international standards; PMI and AACE to review the Program of Works that is submitted by the Contractor. The AACEI has recommended practice. On the site of Ron Winter, he has a list of 100+ things to review in a Program of Works.



You job as a person reviewing the Program of Works is to provide comments on how it is not meeting the Scope, time, cost and any other requirement in the Contract Documents.

It needs a lot of work.



With kind regards,



Samer

Ummmmm...the client is giving contractor a schedule and the manpower loading...



Is it a TA project? Thanks.



R