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Network Diagrams and Resource Utilization
Introduction | Building a Network Diagram | Building an AIB
Manually | AIB Simulation | Resource Constrained Planning |
Resource Leveling | Adding or Modifying Resources | Summary
Introduction
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Last week, we learned more about how to begin planning a
project. We established the project charter, scope statement,
work breakdown structure, and created the activity list. This
week, we will talk about one of the most important aspects of
project management—building a project schedule. We'll use a
tool called a network diagram. There are several ways to build a
network diagram. In this course, we will use the Activity in Box
(AIB) method.
Building a Network Diagram
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Now that we know what needs to be done, we need to sequence
all of the activities and establish a network diagram. With the
concept of a network diagram, you will be able to determine:
(1) a project's scheduled completion time, (2) the slack or float
of project activities, and (3) the critical path of your project.
Depending on the size of the project, the network may be built
in pieces or as a large group. Either way, the step-by-step
process to build a project network is used.
Build a Project Network (or a Partial Network)
1. Brainstorm activities that are required to complete the work
packages, recording those activities on Post-it notes (without
regard to sequencing).
2. Sequence those activities. Determine:
· The order of activities
· Which activities can occur at the same time
· Which activities need dependencies

1. Mandatory: requires the completion of another task.
2. Discretionary: a best practice or convenience. However, the
subsequent task can begin if the discretionary dependency is not
completed.
3. External: from another project or process, such as permits.
4. Internal: dependencies within the control of the project team.
3. Put the notes on a wall using the above information.
4. Build a network using the notes.
Next, the activities are assigned to the people who will be doing
the work. They build duration estimates for the activities. The
most accurate estimates are built using actuals from previous,
similar projects. Then, the activities can be loaded into an
automated scheduling tool like Microsoft Project. At that point,
you will be able to determine the project's scheduled completion
time, the slack or float of project activities, and the critical path
of your project.
Building an AIB Manually
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The good thing about using a tool like Microsoft Project is that
it makes it easy to build a network diagram. The bad thing about
the tool is that it makes it so easy; project managers don't
always understand what they are doing, and cannot see when
they have made a mistake. They just plug in the activities and
move on.
It's like adding—you should first do it manually, and then use a
calculator. Every project manager should know how to build an
AIB manually so that he or she really understands the concepts
before working in Microsoft Project. The project managers who
understand it are much more effective and know how to use the
tools more effectively. Those who do not know how to build a
schedule manually often make mistakes and negatively impact a
project's triple constraints. Practice is required for proficiency.
Just like swimming, scheduling requires practice. You can read
about it, but you must also practice it. Let's start to practice!
When you build the network manually, you will understand the
concepts much better. This demonstration will walk you through

the process of building an AIB manually. You will conduct a
forward pass through a network to determine the early start and
early finish of each activity. A forward pass is moving from
start to finish of the project doing all necessary calculations.
When you complete the forward pass, you know which activity
will be the last one to complete. The Early Finish for that
activity is the earliest date that your project can complete. Next,
you will conduct a backward pass, by moving from finish to
start, to determine the late start and late finish for each activity.
Last of all, you calculate the slack/float for each activity.
Before you begin the AIB Simulation, let's define a few terms.
· Critical Path (CP): By definition, it is the path of activities
from start to finish that all have a slack/float of 0. This path is
especially important because if any of them complete later than
scheduled, your project may not complete on time.
· Early Start (ES): Is the EARLIEST time the activity could
possibly start.
· Early Finish (EF): Is the EARLIEST time the activity could
possibly finish.
· Late Start (LS): Is the LATEST time the activity can start and
not jeopardize the scheduled completion of the project.
· Late Finish (LF): Is the LATEST time the activity can finish
and not jeopardize the scheduled completion of the project.
· Slack/Float or Total Slack/Float: Is calculated by: LF - EF, or
LS - ES (both formulas will result in the same answer; if not,
one of your numbers is incorrect). The slack/float tells you the
number of days/weeks/months that an activity can begin late, or
the number of extra days/weeks/months that an activity can take
without impacting the completion time of the project. However,
this time is shared by all of the activities on a path. If you use
up all of your slack on an activity at the beginning of a path,
subsequent activities will have less slack or no slack.
· Free Slack/Float: This represents how much an activity can
slip without impacting a successor activity. This measure
combined with slack determines which activities receive
priority over resources.

AIB Simulation
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Simulation
Activity in Box Diagram
Welcome to the Bi-Plane 3,000 Project! In this simulation, you
will shadow Sandra, an experienced Project Manager, as she
walks you through the construction of an Activity in Box
Diagram. You will have opportunities to practice both the
Forward and Backward Pass methods in depth. Together, you
will cover the concepts of critical path and float.
Practitioner Corner
In the project management world, you are not likely to hear the
term Activity in Box (AIB) unless you learned your project
management from a textbook. In our world, we use the term
Activity on the Node or AON. The calculations are the same but
the set up is a little different. It is also the method employed by
most project management software. So if you hear the term
AON, network diagramming or precedence diagramming from
project managers, you now know they are all talking about the
same thing.
Resource Constrained Planning
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Now that we have our project schedule established, we need to
align the appropriate resources to accomplish the work. As
resources are applied, conflicts may arise if resources become
over-allocated.
A project manager can address resource conflicts in a variety of
ways, but the first step is to realize there is a conflict. If the
project team builds a schedule using a scheduling tool like
Microsoft Project, the PM can run an Overallocated Resources
report.
Once the over allocation is identified, there are several key
strategies to address them: (1) resource leveling, (2) adding or
modifying resources, and (3) changing the project.
Most methods for addressing resource conflicts cost the project

something, either more money, less functionality, or an
extension in the scheduled completion.
So why bother? In some cases, you have no choice—operational
necessity. For instance, if your company has two bulldozers,
and you need four on a particular week, you will have to
address that resource conflict to complete both projects.
On other projects, resource conflicts take the form of people
being over allocated. Sometimes, a team lead will say that is
what nights and weekends are for but many people would
strongly disagree. If people are overworked, something will
suffer, either the quality of the product will decrease, and
defects and re-work will increase.
Ultimately, it will result in personnel turnover. It costs a project
time and money when people are replaced. If you make people
miserable enough, they will leave either by quitting, getting
sick, transferring, or just not working up to their capacity.
Addressing resource conflicts improves morale, which increases
quality, reduces defects, reduces re-work, decreases team
turnover, and increases team commitment.
Resource Leveling
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The first method—resource leveling is the easiest to do if you
are using an automated scheduling tool like Microsoft Project,
but only if you understand what you are doing. You can also use
the tool to try various what-ifs. For example, try plugging in
new resources and see if their addition will change your
scheduled completion time. If they are not working on a task on
the critical path, their work will not even affect the project's
scheduled completion. One must be careful with auto leveling in
project management software, as it might change the program’s
algorithm associated with the triple constraint.
This method smoothes out the peaks and valleys in your
schedule without increasing your overall budget. If you choose
a level only within available slack as an option when you level
the resources, leveling the resources will not extend your
project's schedule either. However, if there is not enough slack

in your schedule, it will not correct all of your allocation
problems, in which case, you will have to use another method to
relieve the problem.
In summary, the benefits of resource leveling are:
1. Minimizes period-by-period variations by shifting tasks
within their slack
2. Utilizes resources more efficiently
3. Resources do not have days with no work scheduled and other
days with too much work
4. Does not increase budget
5. Does not have to change scheduled completion
Here is an example:
Click on image to enlarge
Before Leveling
After Leveling
Click here for Transcript
Before leveling: The resource is over allocated on 5/2, but not
scheduled to do any work on 5/10. With this schedule, I work
for 16 straight hours on 5/2, and have nothing to do on 5/10.
After leveling: MSP moved the excess work from 5/2 onto 5/10.
With this schedule, I work a regular eight hours each day—
much more palatable! However, as I mentioned before,
sometimes there is not enough slack in the schedule to smooth
out all of your activities, so let's look at some other options.
Adding or Modifying Resources
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Adding people to a project must be approached carefully.
Additional people are easier to absorb into projects that are
well-documented. Adding personnel to well-defined tasks is
straightforward when the plan is clear. Throwing people at
projects that are in trouble, behind, and already managed poorly
often results in an even bigger problem.
Adding resources increases the budget and rarely doubles the
work completed. This is because additional people must be
trained, which ties up their time and the time of a team member
who is training them, and adds to the communication channels.

Modifying resources can take several forms: Assign a person
with greater expertise or more experience to perform or help
with the activity, and increase productivity through improved
methods or technology.
Summary
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Hide and Show
1. What are the different types of dependencies?
Hide Answer
There are four different types of dependencies, including:
Mandatory – requires the completion of another task.
Discretionary – a best practice or convenience. However, the
subsequent task can begin if the discretionary dependency is not
completed.
External – from another project or process.
Internal – dependencies within the control of the project team.
Hide and Show
1.
Hide Answer
The critical path is the path of activities that all have a
slack/float of 0. It is important because if any of them complete
later than scheduled, the project may not be completed on time.
Hide and Show
1. Which tasks would likely be part of the critical path for
building a canoe? Why do the other activities have float/slack?
Hide Answer
1. Obtain wood for boat
2. Build seats
3. Obtain oars or paddles
4. Cut and shape wood for boat body
5. Paint canoe with water sealant
6. Test boat in water

Hide and Show
1. Which tasks would likely be on the critical path for building
a house? Why do the other activities have float/slack?
Hide Answer
1. Obtain bricks
2. Paint Rooms
3. Install furnace
4. Obtain lumber
5. Wire for electricity
6. Obtain building permit
Hide and Show
1. What is float?
Hide Answer
Float is the number of extra days/weeks/months an activity can
take without impacting the completion time of the project. It is
calculated by subtract Earliest Finish Time (EF) from Latest
Finish Time (LF).
Hide and Show
1. Define an activity duration estimate.
Hide Answer
The duration estimate for an activity is the time required to
perform the work plus any associated waiting time.
Hide and Show
1. What are the benefits of resource leveling?
Hide Answer
· Minimizes period-by-period variations by shifting tasks within
their slack Utilizes resources more efficiently
· Resources do not have days with no work scheduled and other
days with too much work.
· Does not increase budget
· Does not have to change scheduled completion
Back to Top

loading
Week 3 Homework: AIB Problems
Before starting this homework assignment, please review the
AIB simulation in this week’s Lecture. This simulation will
provide you with an understanding of how to create a network
diagram, and how to do a forward and backward pass to
determine the ES, LS, EF, LF and slack (float). You will also
learn how to determine the duration of the project, and the
critical path.
In this homework assignment, you will be working through four
Activity In Box (AIB) problems. Using the activity, duration,
and predecessor information given in this document, you should
first construct a network for each "project." [Each problem will
have its own network.]
Once you have constructed the network, please answer the
corresponding questions. Once you answer the questions,
please post your responses to the Drop Box. You do not have to
submit your network diagrams, the answers to the questions are
sufficient.
Once the homework assignment has been graded, the solution
key will be made available. The network diagrams will be
provided, along with the answers to the questions.
Good Luck!

Problem 1
The following data were obtained from a project to create a new
portable electronic.
Activity Duration Predecessors
A 5 Days ---
B 6 Days ---
C 8 Days ---
D 4 Days A, B
E 3 Days C
F 5 Days D
G 5 Days E, F
H 9 Days D
I 12 Days G
Step 1: Construct a network diagram for the project.
Step 2: Answer the following questions: (15 points total)
a) What is the Scheduled Completion of the Project? (5 points)
b) What is the Critical Path of the Project? (5 points)
c) What is the ES for Activity D? (1 points)
d) What is the LS for Activity G? (1 points)
e) What is the EF for Activity B? (1 points)

f) What is the LF for Activity H? (1 points)
g) What is the float for Activity I? (1 points)
Problem 2
The following data were obtained from a project to build a
pressure vessel:
A 6 weeks ---
B 6 weeks ---
C 5 weeks B
D 4 weeks A, C
E 5 weeks B
F 7 weeks D, E, G
G 4 weeks B
H 8 weeks F
I 5 weeks G
J 3 week I
a) Calculate the scheduled completion time. (5 points)

b) Identify the critical path (6 points)
c) What is the slack time (float) for activity A? (1 points)
d) What is the slack time (float) for activity D? (1 points)
e) What is the slack time (float) for activity E? (1 points)
f) What is the slack time (float) for activity G? (1 points)
Problem 3
The following data were obtained from a project to design a
new software package:
A 5 Days ---
B 8 Days ---
C 6 Days A
D 4 Days C, B
E 5 Days A
F 4 Days D, E, G
G 4 Days B, C
H 3 Day G

b) Identify the critical path(s) (6 points)
c) What is the slack time (float) for activity B? (1 points)
f) What is the slack time (float) for activity G? (1 points)
Problem 4
The following data were obtained from an in-house MIS project:

A 5 Days ---
B 8 Days ---
C 5 Days A
D 4 Days B
E 5 Days B
F 3 Day C, D
G 7 Days C, D
H 6 Days E, F, G
I 9 Days E, F
b) Identify the critical path (6 points)
c) What is the slack time (float) for activity A? (1 points)

f) What is the slack time (float) for activity F? (1 points)
1

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