project management in practice, fourth edition prepared by scott m. shafer, updated by william e....
TRANSCRIPT
Project Management in Practice, Fourth Edition
Prepared byScott M. Shafer,
Updated by William E. Matthews and
Thomas G. Roberts, William Paterson University
Copyright 2011 John Wiley & Sons, Inc. 5-1
Mantel, Meredith, Shafer, and Sutton
John Wiley and Sons, Inc.
PERT and CPM
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Program Evaluation and Review Technique (PERT)• U.S. Navy, Booz-Allen Hamilton, and Lockheed Aircraft• probabilistic activity durations
Critical Path Method (CPM)• Dupont De Nemours Inc.• deterministic activity durations
The Language of PERT/CPM
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Activity• a task or set of tasks• uses resources and time
Event• an identifiable state resulting from completion of one
or more activities• consumes no resources or time• predecessor activities must be completed
The Language of PERT/CPM continued
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Milestones• identifiable and noteworthy events that mark
significant progress
Network• a diagram of nodes (activities or events) and arrows
(directional arcs) that illustrate the technological relationships of activities
Path• a series of connected activities between two events
The Language of PERT/CPM concluded
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Critical Path• the set of activities on a path (from the project’s start
event to its finish event) that, if delayed, will delay the completion date of the project
Critical Time• the time required to complete all activities on the
critical path
Building the Network
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There are two ways of displaying a project network
• Activities on Arrows (AOA) network … in which the activities are shown as arrows and events as nodes
• Activities on Nodes (AON) network … in which each task is shown as a node and the technological relationship is shown by the arrows
AON Network Stage 1
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AON Network - Stage 2
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AON Network - Complete
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AOA Network – Stage 1
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AOA network – Stage 2
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AOA Network - Complete
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AOA Network – Showing The Use of a Dummy Task
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Information Contents in an AON Node
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ES EF
ES - Earliest start timeEF - Earliest finish time LS - Latest start timeLF - Latest finish time
LS LF
Activity Activity name duration
Calculating Activity Slack
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Latest Start Time (LS) – Earliest Start Time (ES) = Slack
Latest Finish time (LF) – Earliest Finish time (EF) = Slack
Calculating Probabilistic Activity Times
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The Statistical Distribution of all Possible Times for an Activity
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Activity Expected Time and Variance
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22
E
6
)(Var
6
)(
6
)4(T
ab
ab
bma
95 Percent Level
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Task will be a or lower 5 percent of the time
Task will be b or greater 5 percent of the time
3.3
)( ab
90 Percent Level
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Task will be a or lower 10 percent of the time
Task will be b or greater 10 percent of the time
6.2
)( ab
The Probability of Completing the Project on Time
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2
)(
D
Z
=NORMDIST(D,,,TRUE)
Note: NORMDIST is a function within Excel when using the spreadsheet method
Selecting Risk and Finding D
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2 ZD
NORMINV(probability,,,TRUE)Note: NORMMINV is a function within Excel when using the spreadsheet method
Traditional Statistics Versus Simulations
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Similarity• both procedures assume that task durations are
statistically independent and the paths are independent
Difference• a simulation can circumvent the assumption of
statistical independence by including the activity or path dependencies as part of the model
Gantt Chart of a Sample Project
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Gantt Chart of Sample Project Showing Critical Path, Path Connections, Slack, ES, LS, EF, and LF
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Extensions to PERT/CPM
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Finish to Start (F to S)• finish of Activity A to start of Activity B
Start to Start (S to S)• start of Activity A to start of Activity B
Finish to Finish (F to F)• finish of Activity A to finish of Activity B
Start to Finish (S to F)• start of Activity A to finish of Activity B
Precedence Diagramming Conventions
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Copyright
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Copyright John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work
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