Project Management: A Managerial Approach

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Project Management A Managerial Approach

• Chapter 8 Scheduling

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Overview

• WBS to Schedule Process
• PERT
• Schedule Types
• CPM

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Scheduling

• A schedule is the conversion of a project action
  plan into an operating timetable
• It serves as the basis for monitoring and
  controlling project activity
• Taken together with the plan and budget, it is
  probably the major tool for the management of
  projects

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Scheduling

• In a project environment, the scheduling function
  is more important than it would be in an ongoing
  operation
• Projects lack the continuity of day-to-day
  operations and often present much more complex
  problems of coordination

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Scheduling

• The basic approach of all scheduling techniques
  is to form a network of activity and event
  relationships
• This network should graphically portray the
  sequential relations between the tasks in a
  project
• Tasks that must precede or follow other tasks are
  then clearly identified, in time as well as
  function

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Scheduling

• Such networks are a powerful tool for planning
  and controlling a project and have the following
  benefits
• It is a consistent framework for planning,
  scheduling, monitoring, and controlling the
  project
• It illustrates the interdependence of all tasks,
  work packages, and work elements
• It denotes the times when specific individuals
  must be available for work on a given task

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Scheduling

• Network benefits (cont.)
• It aids in ensuring that the proper
  communications take place between departments and
  functions
• It determines an expected project completion date
• It identifies so-called critical activities that,
  if delayed, will delay the project completion
  time
• It identifies activities with slack that can be
  delayed for specific periods without penalty

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Scheduling

• Network benefits (cont.)
• It determines the dates on which tasks may be
  started - or must be started if the project is to
  stay on schedule
• It illustrates which tasks must be coordinated to
  avoid resource timing conflicts
• It illustrates which tasks may run, or must be
  run, in parallel to achieve the predetermined
  project completion date
• It relieves some interpersonal conflict by
  clearly showing task dependencies

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Simple Schedule Gantt Chart
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Network Techniques PERT and CPM

• With the exception of Gantt charts, the most
  common approach to scheduling is the use of
  network techniques such as PERT and CPM
• The Program Evaluation and Review Technique
  (PERT) was developed by the U.S. Navy in 1958
• The Critical Path Method (CPM) was developed by
  DuPont, Inc during the same time period

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Network Techniques PERT and CPM

• PERT has been primarily used for research and
  development projects
• CPM was designed for construction projects and
  has been generally embraced by the construction
  industry
• The two methods are quite similar and are often
  combined for educational presentation

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Scheduling Terminology

• Activity - A specific task or set of tasks that
  are required by the project, use up resources,
  and take time to complete
• Event - The result of completing one or more
  activities. An identifiable end state occurring
  at a particular time. Events use no resources.
• Network - The combination of all activities and
  events define the project and the activity
  precedence relationships

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Scheduling Terminology

• Path - The series of connected activities (or
  intermediate events) between any two events in a
  network
• Critical - Activities, events, or paths which, if
  delayed, will delay the completion of the
  project. A projects critical path is understood
  to mean that sequence of critical activities that
  connect the projects start event to its finish
  event

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Scheduling Terminology

• An activity can be in any of these conditions
• It may have a successor(s) but no predecessor(s)
  - starts a network
• It may have a predecessor(s) but no successor(s)
  - ends a network
• It may have both predecessor(s) and successor(s)
  - in the middle of a network
• Interconnections from horizontal links in
  vertical WBS

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Hypothetical Network
Calculate t(e) and Z for this network
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Activity and Project Frequency Distributions
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PERT Activity Calculation
t(e) a 4m b a Most Optimistic (MO)
6 m Most Likely (ML) b Most
Pessimistic (MP) t(e) Activity Duration
When a single estimate for activity time is not
sufficient!
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PERT Schedule Probability
Z T(S) T(E) Z Probability of
vSSD(TE)2 Meeting Schedule Z T(S)
T(E) T(S) Scheduled Duration
vSVar(TE) T(E) Critical Path Duration

Z is derived from a table of predetermined
probabilities
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PERT Activity Times Variances
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Variance of Activity Estimates
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Critical Path
TE 30 13 16 5 64 Var(TE) 25 9 1
1 36
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Possible Project Durations
Z (67 64) / v(25 9 1 1) 0.5 Hence,
the probability of meeting the target schedule
(Ts) is 0.69 (69)
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Z Table
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Z-Table Expanded
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Gantt Charts

• The Gantt chart shows planned and actual progress
  for a number of tasks displayed against a
  horizontal time scale
• It is an effective and easy-to-read method of
  indicating the actual current status for each set
  of tasks compared to the planned progress for
  each item of the set
• It can be helpful in expediting, sequencing, and
  reallocating resources among tasks
• Gantt charts usually do not show technical
  dependencies

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Gantt Charts

• There are several advantages to the use of Gantt
  charts
• Even though they may contain a great deal of
  information, they are easily understood
• While they may require frequent updating, they
  are easy to maintain
• Gantt charts provide a clear picture of the
  current state of a project
• They are easy to construct

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Drawing Networks

• Activity-on-Arrow (AOA) networks use arrows to
  represent activities while nodes stand for events
• Activity-on-Node (AON) networks use nodes to
  represent activities with arrows to show
  precedence relationships
• The choice between AOA and AON representation is
  largely a matter of personal preference

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Drawing Networks

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Hypothetical Network
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2
5
6
1
4
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AOA Network Building Blocks
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Partial Koll Business Center - AOA
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Partial AOA Network
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Partial AOA Network
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Full AOA Network
Legend
ActivityDuration
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Activity-on-Node Network Fundamentals