Post on 13-Jan-2016
Chapter 8
Scheduling
© 2012 John Wiley & Sons Inc.
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Useful Abbreviations
CPM - Critical Path MethodPERT - Program Evaluation and Review
Technique
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Network Scheduling Advantage
Consistent frameworkShows interdependencesShows when resources are neededEnsures proper communicationDetermines expected completion date Identifies critical activities
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Network Scheduling Advantage Continued
Shows which of the activities can be delayed
Determines start datesShows which task must be coordinatedShows which task can be run parallelRelieves some conflictAllows probabilistic estimates
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Network Scheduling Techniques: PERT (ADM) and CPM (PDM)
PERT was developed for the Polaris missile/submarine project in 1958
CPM developed by DuPont during the same time
Initially, CPM and PERT were two different approaches– CPM used deterministic time estimates and allowed
project crunching– PERT used probabilistic time estimates
Microsoft Project (and others) have blended CPM and PERT into one approach
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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
Network - The combination of all activities and events that define a project– Drawn left-to-right– Connections represent predecessors
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Terminology Continued
Path - A series of connected activitiesCritical - An activity, event, or path
which, if delayed, will delay the completion of the project
Critical Path - The path through the project where, if any activity is delayed, the project is delayed– There is always a critical path– There can be more than one critical path
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Terminology Continued
Sequential Activities - One activity must be completed before the next one can begin
Parallel Activities - The activities can take place at the same time
Immediate Predecessor - That activity that must be completed just before a particular activity can begin
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Terminology Continued
Activity on Arrow - Arrows represent activities while nodes stand for events
Activity on Node - Nodes stand for events and arrows show precedence
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AON and AOA Format
Figure 8-3
Figure 8-2
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Constructing the Network
Begin with START activityAdd activities without precedences as
nodes– There will always be one– May be more
Add activities that have those activities as precedences
Continue
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Gantt (Bar) Charts
Developed by Henry L. GanttShows planned and actual progressEasy-to-read method to know the current
status
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Advantages and Disadvantage
Advantages– Easily understood– Provide a picture of the current state of a
projectDisadvantage
– Difficult to follow complex projects
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Microsoft Project Gantt Chart
Figure 8-11
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Microsoft Project AON Network
Figure 8-12
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Solving the Network
Table 8-1
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The AON Network from the previous table
Figure 8-13
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Calculating Activity Times
2
22
6
6
4
ab
bmaTE
Beta Distribution
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The Results
Table 8-2
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Critical Path and Time
Figure 8-15
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Critical Path and Time Continued
Figure 8-16
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Slack
Figure 8-16
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Slack Values
Table 8-3
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Precedence Diagramming
Finish to startStart to startFinish to finishStart to finish
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Precedence Diagramming Conventions
Figure 8-17
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Microsoft Projects
Table 8-4
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Gantt Chart
Figure 8-18
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AON Network
Figure 8-19
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Microsoft Project Calendar
Figure 8-23
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Uncertainty of Project Completion Time
Assume activities are statistically independent
Variance of a set of activities is the sum of the individual variances
Interested in variances along the critical path
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Example
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