Schedule Updating and Project Control - Construction Project Scheduling and Control - page 185

under consideration. Six of these methods are as follows (Construction Industry
Institute, 1987b):

1. Units completed: In the units completed method, Percent complete = Units
completed/Total units. This method works well for activities with small, iden-
tical, repetitive components, such as laying bricks or CMUs (concrete masonry
units), excavating, fishing electric wire, installing tile or carpet, and so forth. In
these activities, the type of work and pace are the same throughout the activity.
Percent complete can be calculated simply by dividing units completed by the
total quantity. For example, in an activity involving installing 4,000 concrete
blocks, 1,200 have been installed. Percent complete = 1

000 ∗ 100 =
30%. In some cases, errors may arise despite the similarity in units because of
the effect of learning curves or differing conditions. An example of the sec-
ond case is when a mason is installing block or brick to an 8-ft high wall. The
blocks on the high courses take more time than those in lower courses. When
the error is small, it is ignored.
2. Cost or time ratio: This method applies to those activities that are continuous
and uniform throughout the project, such as Safety Inspection and project
management-type activities. Percent complete is calculated by dividing time
elapsed by total duration (if a time ratio ) or cost to date by total budget (if
a cost ratio ). For example, a project management activity is scheduled for 12
months with a budget of $80,000. After 2 months, it is 2∕12 ∗ 100 = 16

, 200∕4 ,

. 7%

000 ∗ 100 = 25%
complete. Another alternative is the man-hour ratio (actual man-hours con-
sumed divided by total man-hours budgeted). The time ratio method for indi-
vidual activities is similar to the duration percent complete and baseline dura-
tion percent complete methods for calculating the project percent complete.
These methods are discussed in the next section.
3. Start-finish: This method works best for small activities or those with no dura-
tion or a short duration. The project manager may assign one of three stages:
have not started yet (0%), started but not yet finished (an arbitrary amount,
say, 40% or 50%), or finished (100%). Errors usually balance each other. When
these activities become too small, we can look at them as “almost events,”
either 0% or 100% complete.
4. Supervisor's opinion: The most subjective method is the supervisor's opinion
method. It is used when no other method can be suitably applied, such as in
an engine tune-up or dewatering operation. This method relies totally on the
foreman or superintendent's judgment. The contractor may use this method
to exaggerate the percent complete for early payment. Because it does not
require actual measurements, it is considered the quickest (and dirtiest) and
“most convenient” method. The scheduler must be careful not to overuse
this method.
5. Incremental milestones: The incremental milestones method is more suitable
for large and complex or multistage activities. Each stage of a given activity
is assigned a “weight” that is approximately equal to its percentage share of
effort in the total activity. Then, each stage is treated as “all or nothing.” For

complete, or if $20,000 is already spent, it is 20 , 000∕80 ,