© 2006 John Wiley and Sons, Inc. Project Management: A Managerial Approach Chapter 8 – Scheduling

© 2006 John Wiley and Sons, Inc. Overview WBS to Schedule Process PERT Schedule Types CPM

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-1

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-2

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-3

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-4

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-5

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-6

© 2006 John Wiley and Sons, Inc. Simple Schedule – Gantt Chart

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-7

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-8

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-9

© 2006 John Wiley and Sons, Inc. 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 project’s critical path is understood to mean that sequence of critical activities that connect the project’s start event to its finish event Chapter 8-10

© 2006 John Wiley and Sons, Inc. 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

© 2006 John Wiley and Sons, Inc. Hypothetical Network T E =64 Calculate t(e) and Z for this network……

© 2006 John Wiley and Sons, Inc. Activity and Project Frequency Distributions ACTIVITYPROJECT a m b TE (A)(B)

© 2006 John Wiley and Sons, Inc. PERT Activity Calculation t(e) = a + 4m + ba = Most Optimistic (MO) 6m = Most Likely (ML) b = Most Pessimistic (MP) t(e) = Activity Duration When a single estimate for activity time is not sufficient!

© 2006 John Wiley and Sons, Inc. PERT Schedule Probability Z is derived from a table of predetermined probabilities Z = T(S) – T(E)Z = Probability of  SD(T[E]) 2 Meeting Schedule T(S) = Scheduled Duration T(E) = Critical Path Duration

© 2006 John Wiley and Sons, Inc. PERT Activity Times & Variances Activity ambt(e)

© 2006 John Wiley and Sons, Inc. Variance of Activity Estimates Activity ambt(e) [(b-a)/6] 2 Var

© 2006 John Wiley and Sons, Inc. Possible Project Durations T E =64 T S =67

© 2006 John Wiley and Sons, Inc. Z Table Z ValueProbabilityZ ValueProbability

© 2006 John Wiley and Sons, Inc. Z-Table Expanded

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-14

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-16

© 2006 John Wiley and Sons, Inc. 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 Chapter 8-12

© 2006 John Wiley and Sons, Inc. Drawing Networks Chapter 8-13

© 2006 John Wiley and Sons, Inc. Hypothetical Network

© 2006 John Wiley and Sons, Inc. AOA Network Building Blocks 8079 Install software EventActivity

© 2006 John Wiley and Sons, Inc. Partial Koll Business Center - AOA A Application approval D Service availability check C Traffic study B Construction plans

© 2006 John Wiley and Sons, Inc. Partial AOA Network A X C B E (A) A B C X E (B) A B X C E (C)

© 2006 John Wiley and Sons, Inc. Partial AOA Network A B C X E (D) 5 D A B C X E (E) 5 D F ?

© 2006 John Wiley and Sons, Inc. Full AOA Network KOLL BUSINESS CENTER County Engineers Design Department A5A5 B C 10 X Y F 10 G 170 H 35 E 15 D5D5 Activity Duration Legend

© 2006 John Wiley and Sons, Inc. Activity-on-Node Network Fundamentals X Y Z Y and Z are preceded by X Y and Z can begin at the same time, if you wish (B) ABC A is preceded by nothing B is preceded by A C is preceded by B (A) J K L M J, K, & L can all begin at the same time, if you wish (they need not occur simultaneously) All (J, K, L) must be completed before M can begin but XZ AA Y (C) (D) Z is preceded by X and Y AA is preceded by X and Y

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