Schedule Updating and Project Control - Construction Project Scheduling and Control - page 192

Percent Complete and the Computer Software

Computer software packages define their own types of percent complete types. Some
of them are simple and self-explanatory; others are not or are given a peculiar or
misleading title by the software manufacturer. Even worse, some computer software
packages do not give the equations or basis for calculations for such percent com-
plete types. For example, this author had an interesting experience when third-party
reporting software was used, pulling the raw data out of the scheduling software
database. Some activities had percent complete exceeding 100%, although they were
still incomplete. Other activities had negative percent complete! What was interest-
ing was that such numbers showed as 100% and 0% in the reports of the scheduling
software; that is, they were artificially “corrected.” After investigating and contacting
the scheduling software's technical support, the author discovered that equations and
even terminology were used differently in the software. These three equations were
presented earlier:

Percent Complete = Actual Duration∕Total Duration (A)

Percent Complete =(Total Duration − Remaining Duration)∕Total Duration (B)

Percent Complete =(Data Date − Actual Start Date)∕Total Duration (C)

The definition of Total Duration was pivotal: while the software used Original
Duration as Total Duration, the author believes Total Duration = Updated Duration
= Actual Duration + Remaining Duration.
To dramatize this point, suppose that an activity was originally estimated as tak-
ing10 days. For some reason, work has taken much more time than estimated. After
13 days of actual work, it was found that Remaining Duration = 12 days. If we keep
the total duration as the original duration, which is 10 days, we will get the following
results:

With equations A and C , the percent complete is 13∕10 , or 130%

, , .

With equation B the percent complete is (10 − 12)∕10 or − 20%

The real percent complete is 13∕(13 + 12) , or 52%.

Tip Box 7.8

Define type(s) of percent complete to be used in the project, explain them well to the
project stakeholders, and be consistent with using them.