planned, whereas the complete project
finished 29 days early. Moreover, most
of the predecessors of activity 17 were
completed right on time. This means
that the buffers introduced in the planning (see Figure 1) were reduced as well
and appeared to be oversized. In other
words, the start dates of the successor
activities could be advanced, as no organizational constraints (e.g., unavailability of a particular team or subcontractor
until a certain date) occurred. Therefore,
the project was executed even faster
than what would result from shortening
the activity durations alone. Because of
the large fraction of variable costs in the
project, the eventual cost is also reduced
significantly, with a magnitude quite
similar to the reduction in project duration (i.e., 16.6% compared with 18%).
Now reconsider Table 4. This table
shows that it could already be seen from
TP2 that the project was going to be
both under budget and early, as both
the CPI and the SPI(t) were consistently
higher than 1. Again, it becomes clear
that the progress data of TP1 were not
yet reliable, as a CPI of 0.70 and SPI(t)
of 0.41 incorrectly indicated that the
project—when the performance-based
EVM forecasting methods EAC-CPI and
ESM-SPI(t) are applied—was going to
be well over budget, and even more
so, overdue. Furthermore, the RC and
RD values could already be observed
from the last column of Table 4 (i.e., the
post-project forecasts of TP5). Because
the RC and RD represent the actual
project outcomes and, therefore, the
optimal forecast values, they form the
basis for evaluating the accuracy of
the presented cost and time forecasting
methods. More specifically, the mean
absolute percentage error (MAPE) measure is used to this end. The generic
MAPE formula is as follows:
MAPE 5 1 n
n
t51
A2 Ft A
In this formula, A is the actual
(eventual) value and Ft is the forecasted
value at time instance t. In our case,
the time instances t 5 1,...,n represent
to as the real cost (RC) and real dura-
tion (RD) of the project, respectively.
Thus, the project came in more than
€ 40,000 (approximately, US$52,916) or
16.6% under budget and was completed
29 days or 18% earlier compared to the
baseline estimates. Indeed, one can
observe from Table 5 that all critical
activities (i.e., activities 4, 17, 22, and 16)
were completed significantly faster than
planned—especially activity 4, which
took only 22 days instead of 151 days,
and activity 16, which even appeared to
be superfluous (i.e., no adjustments to
the furniture were needed). The critical
activity for which the duration was least
reduced is activity 17. Notice that this
activity was only 19 days shorter than
Results and Discussion
The considered project was executed
and exhibited the real activity outcomes
presented in the two last columns of
Table 5. The baseline costs and durations (i.e., the as-planned values) in the
second and third columns were already
shown in Table 1, but are again included
here to allow for easier comparison.
Furthermore, the project totals for baseline costs and durations are, of course,
the BAC and PD, respectively.
On the project level, an eventual cost of €203,606 (approximately,
US$269,350) and eventual duration of
132 days were reached (see the two last
columns of project total in Table 5). From
now on, these outcomes are referred
ID Activity Name
Baseline
Cost [€]
Baseline
Duration [d]
Real
Cost [€]
Real
Duration [d]
1 Fixed ceilings 2, 129 89 1,929 22
2 Metal ceilings 19,509 89 20,190 62
4 Movable partition walls ( 1) 37,641 151 33,605 22
6 Plaster walls 36,184 22 34, 103 81
9 Full subcontracting ( 1) 1,079 1 847 1
10 Disassembling ceilings 2,509 7 2,277 7
12 Adjusting raised floor 1,800 3 1,459 3
11 Placing carpet 27,162 5 21,457 5
21 Full subcontracting ( 2) 20,068 67 15,694 22
13 Placing furniture 36,023 3 29,191 3
14 Placing glass walls 180 1 178 1
3 Acoustic dams 1,674 2 1,520 2
20 Movable partition walls ( 2) 4,926 9 3,245 9
5 Movable partition walls ( 3) 619 9 615 9
7 Doors 6,259 3 5,529 3
8 Joinery 1,964 3 1,783 3
17 Painting works 8,538 41 6,185 22
19 Ancillary works 16,619 3 1,374 3
15 Finishings 13, 132 71 11,920 65
22 Miscellaneous 998 77 906 22
16Adjustingfurniture 312 61 0 0
18 Moving reinforcing screens 4,879 3 905 3
23 Additional work 0 0 8,695 85
Project total 244,205 161 203,606 132
Table 5: Baseline and real activity costs and durations for the considered project.