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Chapter 9 1. 1.Understand and apply key scheduling terminology. 2.Apply the logic used to create activity networks, including predecessor and successor.

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Presentation on theme: "Chapter 9 1. 1.Understand and apply key scheduling terminology. 2.Apply the logic used to create activity networks, including predecessor and successor."— Presentation transcript:

1 Chapter 9 1

2 1.Understand and apply key scheduling terminology. 2.Apply the logic used to create activity networks, including predecessor and successor tasks. 3.Develop an activity network using Activity-on-Node (AON) techniques. 4.Perform activity duration estimation based on the use of probabilistic estimating techniques. 5.Construct the critical path for a project schedule network using forward and backward passes. 6.Identify activity float and the manner in which it is determined. 7.Understand the steps that can be employed to reduce the critical path. 2

3  Project scheduling requires us to follow some carefully laid-out steps, in order, for the schedule to take shape.  Project planning, as it relates to the scheduling process, has been defined by the PMBoK as: ◦ “The identification of the project objectives and the ordered activity necessary to complete the project including the identification of resource types and quantities required to carry out each activity or task.” 3

4  Represents the conversion of project goals into an achievable methodology.  Creates a timetable and reveals the network logic that relates project activities to each other.  A graphical set of sequential relationships between project task which, when performed, result in the completion of the project goals.  Vitally important to obtaining project goals, being on time and on budget. 4

5  Allows project teams to use a method for planning and scheduling  There are several advantages when project networks and scheduling are done well 5 Show interdependence Facilitate communication Help schedule resources Identify critical activities Determine project completion Show start & finish dates for task See slide 26 for an example

6 6  Successors  Predecessors  Network diagram  Serial activities  Concurrent activities E D C B A F  Merge activities  Burst activities  Node  Path  C ritical Path

7 7 The same mini-project is shown with activities on arrow… C E D B F E C D B F …and activities on node. AOA vs. AON

8 1.Some determination of activity precedence ordering must be done prior to creating the network. 2.Network diagrams usually flow from left to right. 3.An activity cannot begin until all preceding connected activities have been completed. 4.Arrows on networks indicate precedence and logical flow. Arrows can cross over each other, although it is helpful for clarity’s sake to limit this effect when possible. 5.Each activity should have a unique identifier associated with it (number, letter, code, etc.). 6.Looping, or recycling through activities, is not permitted. 7.Although not required, it is common to start a project on a single node. A single node point also is typically used as a project end indicator. 8

9 Information for Network ConstructionName: Project Delta ActivityDescriptionPredecessors AContract signingNone BQuestionnaire designA CTarget market IDA DSurvey sampleB, C EDevelop presentationB FAnalyze resultsD GDemographic analysisC HPresentation to clientE, F, G Construct a Network Diagram 9

10 10 A Contract C Market ID B Design G Demog. E Dev. Present. D Survey F Analysis H Present

11  College research paper example 11

12 12 Activity A Activity B Activity C Activity D Activity C Activity B Activity A Activity D

13 13 Early Start Activity Float Activity Descriptor Late Start ID Number Activity Duration Late Finish Early Finish 11 D 24 0 Survey ES ID EF Slack Task Name LS Duration LF

14 14  Assumptions ◦ Based on normal working methods during normal hours ◦ Durations are always somewhat uncertain ◦ Timeframes can be from minutes to weeks  Methods ◦ Past experience ◦ Expert opinion ◦ Mathematical derivation based on Beta Distribution  Most optimistic (a) time – better then planned  Most likely (m) time – realistic expectation  Most pessimistic (b) time – Murphy’s Law kicks in There are only two types of estimates…lucky and wrong.

15  Critical Path Method (CPM) assumes we know a fixed time estimate for each activity and there is no variability in activity times  Program Evaluation and Review Technique (PERT) uses a probability distribution for activity times to allow for variability 15

16 Where: a = Most optimistic time m = Most likely time b = Most pessimistic time 16

17  Project variance is computed by summing the variances of activities on the critical path Project variance =  (variances of activities on critical path) Project standard deviation = Project Variance 17

18 TaskPredecessorambmeanvariance Z YZ XZ WY, X VW TW ST, V Determine the expected duration and variance of each activity. 2.Sketch the network described in the table. 3.Determine the expected project time and standard deviation. 18

19 19  Forward pass – an additive move through the network from start to finish  Backward pass – a subtractive move through the network from finish to start  Critical path – the longest path from end to end which determines the shortest project length

20 ActivityDescriptionPredecessorsEstimated Duration AContract signingNone5 BQuestionnaire designA5 CTarget market IDA6 DSurvey sampleB, C13 EDevelop presentationB6 FAnalyze resultsD4 GDemographic analysisC9 HPresentation to clientE, F, G2 20 Construct the critical path.

21 21 A Contract 5 B Design 5 C Market ID 6 D Survey 13 G Demog. 9 F Analysis 4 E Dev. Present 6 H Present 2 Critical Path is indicated in bold

22 22 Forward Pass Rules (ES & EF) ◦ ES + Duration = EF ◦ EF of predecessor = ES of successor ◦ Largest preceding EF at a merge point becomes ES for successor Backward Pass Rules (LS & LF) ◦ LF – Duration = LS ◦ LS of successor = LF of predecessor ◦ Smallest succeeding LS at a burst point becomes LF for predecessor ES ID EF Slack Task Name LS Duration LF Calculate the forward/backwards pass.

23 23 0 A 5 Contract 5 5 B 10 Design 5 5 C 11 Market ID 6 11 D 24 Survey G 20 Demograph F 28 Analysis 4 10 E 16 Dev. Present 6 28 H 30 Presentation 2 ES ID EF Slack Task Name LS Duration LF

24 24 0 A 5 Contract B 10 Design C 11 Market ID D 24 Survey G 20 Demograph F 28 Analysis E 16 Dev. Present H 30 Presentation ES ID EF Slack Task Name LS Duration LF

25  Informs us of the amount an activity can be delayed without delaying the overall project.  It is determined as a result of performing the forward and backward pass through the network.  Calculated either by ◦ LF-EF = Slack ◦ LS-ES = Slack  The critical path is the network path with “0” slack.* ◦ *This assumes a deadline has not been set for LF that is within our calculated project time. ◦ *Negative float is a result of the project time being longer than a set project end time. 25 Calculate the slack time and determine critical path.

26 26 0 A 5 0 Contract B 10 1 Design C 11 0 Market ID D 24 0 Survey G 20 8 Demograph F 28 0 Analysis E Dev. Present H 30 0 Presentation ES ID EF Slack Task Name LS Duration LF Critical Path is indicated in bold

27 TaskPredecessorTime A--4 BA9 CA11 DB5 EB3 FC7 GD, F3 HE, G2 KH1 1.Sketch the network described in the table. 2.Determine the ES, LS, EF, LF, and slack of each activity. 3.Determine the critical path. 27

28 28  Project ABC can be completed more efficiently if subtasks are used.  Example: A does not need to be completely finished before work on B starts. A(3)B(6)C(9) ABC=18 days Laddered ABC=12 days A 1 (1)A 2 (1)A 3 (1) B 1 (2)B 2 (2)B 3 (2) C 1 (3)C 2 (3)C 3 (3)

29 29 Used as a summary for subsets of activities 0 A B C Hammock Useful with a complex project or one that has a shared budget

30  Eliminate tasks on the critical path ◦ remove task with no value  Convert serial paths to parallel when possible  Overlap sequential tasks ◦ use laddering when possible  Shorten the duration on critical path tasks  Shorten ◦ early tasks (have you read “The Goal”) ◦ longest tasks ◦ easiest tasks ◦ tasks that cost the least to speed up – “crashing” 30

31 1.Define the following terms: Path, Activity, Early start, Early finish, Late start, Late finish, Forward pass, Backward pass, Node, AON, Float, Critical Path, PERT 2.Distinguish between serial activities and concurrent activities. Why do we seek to use concurrent activities as a way to shorten a project’s length? 3.List three methods for deriving duration estimates for project activities. What are the strengths and weaknesses associated with each method? 31

32 4.In your opinion, what are the chief benefits and drawbacks of using beta distribution calculations (based on PERT techniques) to derive activity duration estimates? 5.“The shortest total length of a project is determined by the longest path through the network.” Explain the concept behind this statement. Why does the longest path determine the shortest project length? 6.The float associated with each project task can only be derived following the completion of the forward and backward passes. Explain why this is true. 32

33  Now that Joe has agreed to your WBS, he wants to review a schedule and present it to the president. She is a “big picture” thinker and does not usually get involved with the details, so Joe wants to limit the content of the diagram you show her to the basics that concern her.  You have also worked with your team on estimating the durations of each of the work packages in the WBS. Note that in this case, the work packages are the scheduled activities. Here is your current plan for the briefing to the president: 33

34 34

35 1.Build a network diagram 2.Calculate forward pass, backward pass, float, and critical path 3.Be ready to address— ◦ How long will the project take? ◦ When should you begin installing new furniture, communications equipment, and computers if you want to be in the new office by July 31? ◦ What items are on the critical path? 35


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