AN APPROACH TO PERFORM PROJECT PERT ANALYSIS MANUALLY
One - Point estimation reflects one estimate per activity. It is based on expert judgment,
experience, expert opinion or historical information. Fear of padding is always lies with onepoint estimation. Also it does not reflect risk or uncertainties associated to estimation. Therefore
Three-point estimation is preferred for activity duration and cost estimation. There-point
estimation ‘PERT’ uses pessimistic (P), most likely (M) and optimistic (O) for estimation. PERT
is also called as ‘Weighted Average’ (not just an average). It is calculated by a formula:
PERT =
Author’s Profile:
Yasir Masood- PMP
Bsc Mechanical, Msc
PERT provides the basis to calculate Activity Standard Deviation, Activity Variance and Project
Variance and Project Standard Deviation.
Mechatronics Engg.
Expertise:
Activity Standard Deviation =
Project Management,
Project Planning, Project
Activity Variance =
Risk Management,
Engineering Solutions,
Project Variance =
Statistical Analysis &
Engineering Software
Project Standard Deviation
=
Let’s take an example of a ‘Pressure Vessel Design and Commissioning Project’ to enlighten
PERT Analysis. Assume that there are four phases in a project i.e. design, fabrication, testing and
commissioning. Client has given 70 days to complete the project. Project planning team asses the
duration of project phases as given below:
Duration
Optimistic
S.No.
Project Phases
Most
Likely
(O)
Pessimistic
PERT
(P)
Activity
Standard
Deviation
Variance
Project
Variance
Project
Standard
Deviation
(M)
Software Skills:
Primavera
P6,
P5,
Pertmaster, Ms Project,
WBS Chart pro, Oracle
CrystalBall,
Palisade
@Risk,
AutoCAD,
SolidWorks,
Floworks,
Ms Office, Ms Visio,
SmartDraw,
Camtasia
etc.
1
Design
10
15
20
15.00
1.67
2.78
2
Fabrication
20
25
35
25.83
2.50
6.25
3
Testing
5
8
10
7.83
0.83
0.69
4
Commissioning
10
18
25
17.83
2.50
6.25
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http://mechint.wordpress.com
15.97
3.995
Table -1: PERT Analysis
gE n g r . Y a s i r M a s o o d – P M P , M P M I , M P M I - A G C ( y a s i r 9 1 1 0 9 @ g m a i l . c o m )
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According to calculations, project will be completed in 66.60 ~67 days. It portrays the project
will be completed before the deadline. Wow sounds great! Is it the real story? Would it be the
only information to rely on? Answer is no, project completion depicts only the one facade of
the situation. Perhaps one requires more calculations to have a complete picture of a scenario.
Therefore it is required to first find out the probability to meet the deadline on the basis of
planning. Probability to finish project on deadline of 70 days can be found by ‘Z’ (Standard
Normal Equation). Where ‘Z’ is the number of standard deviations the due date or target date
lies from the mean or expected date. Project Standard Deviation
is already calculated
3.995~4 days. So in order to calculate the probability, the standard normal equation can be
applied as follows:
Author’s Profile:
Yasir Masood- PMP
Bsc Mechanical, Msc
Mechatronics Engg.
Z=
Expertise:
= (70 days – 67 days)/4 days
Project Management,
Project Planning, Project
= 0.75
Risk Management,
Now referring to ‘Normal Curve Area Table’* to find out the area under the normal curve. From
table, the probability is found 0.77337. Thus there is 77.337% chance that ‘Pressure Vessel
Design and Commissioning Project’ can be completed in 70 days or less.
What if to know the 99 % probability to meet the deadline? 99% chance to complete the project
can be calculated by formula as given below:
Due Date =
Engineering Solutions,
Statistical Analysis &
Engineering Software
Software Skills:
Primavera
P6,
P5,
Pertmaster, Ms Project,
= 67 + 2.33** *4
W BS Chart pro, Oracle
CrystalBall,
= 67 + 9.32
= 76.32 ~ 76 Days
Palisade
@Risk,
AutoCAD,
SolidWorks,
Floworks,
Ms Office, Ms Visio,
PERT Analsis shows there is a requirement to compress the schedule at least 6 days to meet the
client’s deadline
SmartDraw,
Camtasia
etc.
Blog:
http://mechint.wordpress.com
* Normal Curve Area Table is also called as Distribution Table.
** At 2.33 in Normal Curve Area Table the probability is approximately 99%.
gE n g r . Y a s i r M a s o o d – P M P , M P M I , M P M I - A G C ( y a s i r 9 1 1 0 9 @ g m a i l . c o m )
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