MIS Project
Management
Chapter 4
Lecturer
Sihem Smida
Developing a project
plan
Developing the Project Plan
‫محذوفة‬
• The Project Network
–A flow chart that graphically depicts the sequence,
interdependencies, and start and finish times of the
project job plan of activities that is the critical path
through the network.
• Provides the basis for scheduling labor and equipment.
• Enhances communication among project participants.
• Provides an estimate of the project’s duration.
• Provides a basis for budgeting cash flow.
• Identifies activities that are critical.
• Highlights activities that are “critical” and can not be delayed.
• Help managers get and stay on plan.
6–2
Constructing a Project Network
• Terminology
–Activity: an element of the
project that requires time.
A
–Merge Activity: an activity that
has two or more preceding
activities on which it depends.
B
–Parallel (Concurrent) Activities:
Activities that can occur
independently and, if desired,
not at the same time.
D
C
6–3
Constructing a Project Network (cont’d)
‫محذوفة‬
Terminology
–Path: a sequence of connected, dependent activities.
–Critical path: the longest path through the activity
network that allows for the completion of all projectrelated activities; the shortest expected time in which
the entire project can be completed. Delays on the
critical path will delay completion of the entire project.
C
A
B
D
(Assumes that minimum of A + B > minimum of C in length of times to complete activities.)
6–4
Constructing a Project Network (cont’d)
• Terminology
–Event: a point in time when an activity is started
or completed. It does not consume time.
–Burst Activity: an activity that has more than one
activity immediately following it (more than one
dependency arrow flowing from it).
• Two Approaches
B
–Activity-on-Node (AON)
• Uses a node to depict an activity.
A
C
–Activity-on-Arrow (AOA)
• Uses an arrow to depict an activity.
D
6–5
Basic Rules to Follow in Developing
Project Networks
‫محذوفة‬
1. Networks typically flow from left to right.
2. An activity cannot begin until all preceding
connected activities are complete.
3. Arrows indicate precedence and flow
and can cross over each other.
4. Each activity must have a unique identify number
that is greater than any of its predecessor activities.
5. Looping is not allowed.
6. Conditional statements are not allowed.
7. Use common start and stop nodes.
6–6
Network Computation Process
‫محذوفة‬
• Forward Pass—Earliest Times
–How soon can the activity start? (early start—ES)
–How soon can the activity finish? (early finish—EF)
–How soon can the project finish? (expected time—ET)
• Backward Pass—Latest Times
–How late can the activity start? (late start—LS)
–How late can the activity finish? (late finish—LF)
–Which activities represent the critical path?
–How long can activity be delayed? (slack or float—SL)
6–7
Forward Pass Computation
‫محذوفة‬
• Add activity times along each path in the
network (ES + Duration = EF).
• Carry the early finish (EF) to the next activity
where it becomes its early start (ES) unless…
• The next succeeding activity is a merge activity,
in which case the largest EF of all preceding
activities is selected.
6–8
Backward Pass Computation
‫محذوفة‬
• Subtract activity times along each path in the
network (LF - Duration = LS).
• Carry the late start (LS) to the next activity
where it becomes its late finish (LF) unless
• The next succeeding activity is a burst activity,
in which case the smallest LF of all preceding
activities is selected.
6–9
Determining Free Slack (or Float)
‫محذوفة‬
• Free Slack (or Float)
–Is the amount of time an activity can be delayed after
the start of a longer parallel activity or activities.
–Is how long an activity can exceed its early finish date
without affecting early start dates of any successor(s).
–Allows flexibility in scheduling scarce resources.
• Sensitivity
–The likelihood the original critical path(s) will change
once the project is initiated.
–The critical path is the network path(s) that has (have)
the least slack in common.
6–10
Project Management Example:
General Foundry Inc.
‫محذوفة‬
• Have 16 weeks to install a complex air filter
system on its smokestack
• May be forced to close if not completed w/in 16
weeks due to environmental regulations
• Have identified 8 activities
AON Network for General Foundry
Activity Time Estimates
Determining the Project Schedule
‫محذوفة‬
• Some activities can be done simultaneously so
project duration should be less than 25 weeks
• Critical path analysis is used to determine
project duration
• The critical path is the longest path through the
network
Critical Path Analysis
‫محذوفة‬
Need to find the following for each activity:
• Earliest Start Time (EST)
• Earliest Finish Time (EFT)
• Latest start time (LST)
• Latest Finish Time (LFT)
• EFT Rule:
EFT = EST + activity time
Node Notation:
Forward Pass: Earliest Start and Finish
Times
• LST Rule:
LST = LFT – activity time
Slack Time and Critical Path(s)
‫محذوفة‬
• Slack is the length of time an activity can be
delayed without delaying the project
Slack = LST – EST
• Activities with 0 slack are Critical Activities
• The Critical Path is a continuous path through the
network from start to finish that include only critical
activities
Project Schedule and Slack Times
Critical Path and Slack Times
Total Slack Time vs. Free Slack Time
‫محذوفة‬
• Total slack time is shared by more than 1
activity
Example: A 1 week delay in activity B will leave
0 slack for activity D
• Free slack time is associated with only 1 activity
Example: Activity F has 6 week of free slack time
Variability in Activity Times
•
•
‫محذوفة‬
Activity times are usually estimates that are
subject to uncertainty
Approaches to variability:
1. Build “buffers” into activity times
2. PERT – probability based
3. Computer simulation
PERT Analysis
‫محذوفة‬
• Uses 3 time estimates for each activity
Optimistic time (a)
Pessimistic time (b)
Most likely time (m)
• These estimates are used to calculate an
expected value and variance for each activity
(based on the Beta distribution)
• Expected activity time (t)
t = (a + 4m + b)
6
• Variance = [ (b – a) / 6 ]2
• Standard deviation = SQRT(variance)
= (b – a)
6
Activity Information
Activity
A
B
C
D
E
F
G
H
Time estimates (wks)Mean Time
a
m
b
t
1
2
1
2
1
1
3
1
2
3
2
4
4
2
4
2
3
4
3
6
7
9
11
3
2
3
2
4
4
3
5
2
Variance
s2
0,111
0.111
0.111
0.444
1.000
1.778
1.778
0.111
27
Network Diagram with Expected Activity
Times and Variances
[3,
1,778]
[2,
0.111]
[2,
0.111]
[4,
1.000]
[2,
0.111]
[5,
1,778]
[3,
0.111]
[4,
0.444]
6–28
Earliest start / Earliest Finish
4
0
0
2
2
4
4
0
3
0
3
7
8
13
15
7
8
13
6–29
Latest start / Latest Finish
10
0
0
2
2
4
4
0
4
1
4
13
8
13
15
8
8
13
6–30
Project Variance and Standard
Deviation
• Project variance (σp2)
= ∑ (variances of all critical path activities)
σp2 = 0.11 + 0.11 + 1.0 + 1.78 + 0.11
= 3.11
• Project standard deviation (σp)
= SQRT (Project variance)
σp = SQRT ( 3.11) = 1.76
Probability of Project Completion
• What is the probability of finishing the project
within 16 weeks?
• Assumptions:
– Project duration is normally distributed
– Activity times are independent
• Normal distribution parameters:
μp = expected completion time= 15 weeks
σp = proj standard deviation = 1.76 weeks
Probabilistic Network Analysis
Determine the probability that a project is
completed (project completion time is )
within a specified period of time
x-m
Z =
where
s
m = tp = project mean time
s = project standard deviation
x = project time (random variable)
Z = number of standard deviations of x from
the mean (standardized random variable) 
33
Normal Probability Calculations
Z = (Target time – expected time)
σp
Z = (16 - 15) = 0.57
1.76
This means 16 weeks is 0.57 standard deviations
above the mean of 15 weeks.
Probability Based on
Standard Normal Table
Prob (proj completion < 16 weeks) = 0.7158
Project Duration for
a Given Probability
• What project duration does General Foundry
have a 99% chance of completing the project
within?
i.e. Prob (proj duration < ? ) = 0.99
• From Std. Normal Table, this corresponds to Z =
2.33
Z = (? - 15) = 2.33
1.76
So ? = 15 + 2.33 x 1.76 = 19.1 weeks
Practical Considerations
• Network Logic Errors
• Activity Numbering
• Use of Computers to
Develop Networks
• Calendar Dates
• Multiple Starts and
Multiple Projects
6–38
Project Time Management Processes
• Activity definition: identifying the specific activities/tasks
that the project team members and stakeholders must
perform to produce the project deliverables
• Activity sequencing: identifying and documenting the
relationships between project activities
• Activity resource estimating: estimating how many
resources a project team should use to perform project
activities
• Activity duration estimating: estimating the number of
work periods that are needed to complete individual
activities
• Schedule development: analyzing activity sequences,
activity resource estimates, and activity duration estimates
to create the project schedule
• Schedule control: controlling and managing changes to
the project schedule
39
Project Time Management
Activity Lists and Attributes
• An activity list is a tabulation of activities to be
included on a project schedule that includes:
–The activity name
–An activity identifier or number
–A brief description of the activity
• Activity attributes provide more information
such as predecessors, successors, logical
relationships, leads and lags, resource
requirements, constraints, imposed dates, and
assumptions related to the activity
40
Project Time Management
Step1: activity definition
Inputs
Decomposition
Templates
Level of detail
Expert judgement
Work breakdown
structure and
dictionary
Project scope
statement
Project
management
plan
Activity
definition
Tools & Techniques
Activity
sequency
Activity
resource
estimating
Outputs
Activity list
Work breakdown
structure and
dictionary
(updates)
Activity
duration
estimating
Schedule
development
Schedule
control
Step2: activity sequency
Inputs
Precedence
Diagramming Method
(PDM)
Arrow Diagramming
Method (ADM)
Schedule network
templates
Dependency
determination.
Activity list
Project scope
statement
Activity
definition
Tools & Techniques
Activity
sequency
Activity
resource
estimating
Activity
duration
estimating
Outputs
Project schedule
network diagrams
Activity list
(updates)
Project
management plan
and scope
statement
(updates)
Schedule
development
Schedule
control
Step3: activity resource estimating
Inputs
Expert judgement
Alternative
identification
Published estimating
data
Estimating software
programs
Bottom-up estimates
by activity
Activity list
Activity list
attributes
Organizational
policies
Resource
availability
Activity
definition
Tools & Techniques
Activity
sequency
Activity
resource
estimating
Activity
duration
estimating
Outputs
Activity resource
requirements
Resource
requirements
supporting detail
Activity list
(updates)
Schedule
development
Schedule
control
Step4: activity duration estimating
Inputs
Activity list
Activity list
attributes
Project scope
statement
Project cost
estimates
Activity resource
requirements
Resource
availability
Organizational
process assets
Risk register
Activity
definition
Activity
sequency
Tools & Techniques
Expert judgements
analogous duration
estimating
quantitatively based
durations
three-point-estimates of
duration
reserve time
maximum activity duration
Activity
resource
estimating
Activity
duration
estimating
Outputs
Activity duration
estimates
Activity list
(updates)
Activity list
attributes
(updates)
Schedule
development
Schedule
control
Step5: schedule development
Inputs
Project scope
statement
Project schedule
network diagrams
Activity duration
estimates
Activity resource
requirements
Resource
availability
Risk register
Activity list
attributes
Resources
calendars
Activity
definition
Activity
sequency
Tools & Techniques
Expert judgements
analogous duration
estimating
quantitatively based
durations
three-point-estimates of
duration
reserve time
maximum activity duration
Activity
resource
estimating
Activity
duration
estimating
Outputs
Critical path
method
Schedule
compression
Resource
leveling
Schedule
development
Schedule
control
Step6: schedule control
Inputs
Project schedule
Performance
reports
Approved change
requests
management plan
Activity
definition
Activity
sequency
Tools & Techniques
Outputs
Progress reporting
schedule charge control
system
performance measurement
project management
software
variance analysis
schedule comparison bar
charts
Activity
resource
estimating
Activity
duration
estimating
Project scheduel
(updates)
Requested
changes
Recommended
corrective action
Organizational
process assets
Schedule
development
Schedule
control