PERT Charts
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Transcript of PERT Charts
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PERT Charts
Prepared by: Michael Palazzo
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What are PERT Charts?OPERT stands for Program
Evaluation and Review Technique
OTo understand what a PERT chart is, we must first learn the Critical Path Method (CPM)
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CPM
ODeveloped as a network model for project management
OUses a fixed time estimate for each activity
OEasy to understand but does not account for time variations of activities
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What is PERT?ODeveloped in late 1950’s
OA network model that allows for randomness in activity completion times
OHas potential to reduce time and cost to complete a project
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Network DiagramsOPERT Charts use network diagrams
OActivities and milestones of a project are represented by arcs and nodes on a model
OPERT was originally Activity-on-Arc diagram
OSome now use Activity-on-Node
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Arc vs. Node
Activity-on-arc network:
Activity-on-node network:
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Example of a PERT Chart
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6 Steps
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Identify/Determine Activity Sequence
O Identify Activities and Milestones:O Activities are tasksO Milestones mark beginning and end
of activities
ODetermine Activity Sequence:O Sequence is evident for someO Others require more analysis
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ConstructOConstruct the Network Diagram:
O Create diagram with activity sequence info
O For activity-on-arc model, activities are arrowed lines and milestones are circles
O Software exists to simplify this step
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EstimateOEstimate Activity Times:
O Weeks are commonly used as unit of time
O PERT is able to deal with uncertainty in activity completion times
O Each activity in model includes three time estimates
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Estimate Continued…OOptimistic Time:
O Shortest time activity can be completed
OMost Likely Time:O Completion time with highest probability
OPessimistic Time:O Longest time the activity might require
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Determine Critical Path
OCritical path is longest path in project
ODetermined by adding the times for activities in each sequence
OBy accelerating activities on critical path you decrease total project time
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UpdateOUpdate as Project Progresses:
O Make adjustments to PERT chart as project continues
O Resources may need to be added to stay on schedule if there are delays
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Benefits of PERT
OGives expected project completion time
OProvides probability of completion before a date
OShows critical path activities
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Benefits Continued…
OProvides activity start and end dates
OShows activities that have slack time
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Limitations of PERT
OThe activity time estimates are subjective
OPERT assumes a beta distribution for its time estimates; actual distribution may be different
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Limitations Continued…
OConsistently underestimates the expected project completion timeO PERT assumes probability distribution
of project completion time is same as critical path
O If delayed, other paths can become critical path
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ReferencesO Pert Charts:
http://www.netmba.com/operations/project/pert/
O More Information on CPM/CPA:http://www.mindtools.com/critpath.html
O PERT Chart Images:http://en.wikipedia.org/wiki/Program_Evaluation_and_Review_Techniquehttp://cpmtutor.com/c05/fp-dummies.htmlhttp://cnx.org/content/m32170/latest/
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Thank you for your attention!