Slides by: Ms. Shree Jaswal

Slides by: Ms. Shree Jaswal

Introduction developing the project schedule Scheduling Charts logic diagrams and network (AOA,AON) critical path calendar scheduling and time based network management schedule reserve PDM network, PERT CPM Resource loading, resource leveling allocating scarce resources to projects and several projects Goldratt s critical chain. Chapter 4 Slides by: Ms. Shree Jaswal 2

Textbook: * Chp 7: The Project's Schedule and budget Reference Books: #1 Chp 7: Network Scheduling and PDM #1 Chp 8:PERT, CPM, Resource Allocation and GERT #1 Chp 9: Cost estimating and budgeting #1 Chp 10:Managing risks in projects #2 Chp 8:Project Activity Scheduling Note: * Textbook: "Information Technology Project Management" Jack T. Marchewka #1 Reference book: "Project Management for business and Technology" John M. Nicholas #2 Reference book: "Project Management" Jack R. Meredith Chapter 4 Slides by: Ms. Shree Jaswal 3

Chapter 4 Slides by: Ms. Shree Jaswal 4

Activity definition Activity sequencing Activity duration estimation Schedule development Schedule control Chapter 4 Slides by: Ms. Shree Jaswal 5

Project Management Tools Gantt Charts Project Network Diagrams Activity on the Node (AON), Activity on arrow (AOA) Critical Path Analysis Pert Precedence Diagramming Method (PDM) Chapter 4 Slides by: Ms. Shree Jaswal 6

Simplest and most commonly used scheduling technique The chart consists of horizontal scale divided into time units-days, weeks or months and vertical scale showing project work elements. Chapter 4 Slides by: Ms. Shree Jaswal 7

Advantages: Gives a clear pictorial model of the project. Simplicity for the planner and the user. Easy to construct & understand. Is a means for assessing the status of individual work elements and the project as a whole. It can be used as Expense Charts 1.for labor planning 2.resource allocation 3.budgeting Chapter 4 Slides by: Ms. Shree Jaswal 8

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Drawbacks: It does not explicitly show interrelationships among work elements. Gantt charts are often maintained manually. This is easy task in small projects, but is burdensome and a disadvantage in large projects; it causes apathy and results in charts becoming outdated. Chapter 4 Slides by: Ms. Shree Jaswal 13

Activity Start time Duration A 0 5 B 6 3 C 7 4 D 8 5 Chapter 4 Slides by: Ms. Shree Jaswal 14

Gantt charts Activities 0 6 12 18 24 30 Chapter 4 Slides by: Ms. Shree Jaswal Time 15

Suppose C & D must start only after activity B is completed. Chapter 4 Slides by: Ms. Shree Jaswal 16

Gantt charts Activities 0 6 12 18 24 30 Chapter 4 Slides by: Ms. Shree Jaswal Time 17

Gantt charts don t explicitly show task relationships don t show impact of delays or shifting resources well network models clearly show interdependencies Chapter 4 Slides by: Ms. Shree Jaswal 18

network of relationships research what s been done research what needs doing internet research pick final topic write print elements & relationships (sequence) this is ACTIVITY-ON-NODE can have ACTIVITY-ON-ARC Chapter 4 Slides by: Ms. Shree Jaswal 19

Activity on node diagrams A,6 B,9 Chapter 4 Slides by: Ms. Shree Jaswal 20

Activity on arc or arrow 1 2 3 Chapter 4 Slides by: Ms. Shree Jaswal 21

Activity Duration Immediate Predecessor A 6 _ B 9 A C 8 A D 4 B,C E 6 B,C Duration is given in weeks Chapter 4 Slides by: Ms. Shree Jaswal 22

AON diagram corresponding to data in prev table B,9 D,4 Start A,6 Finish C,8 E,6 Critical path A-B-E:21 weeks Chapter 4 Slides by: Ms. Shree Jaswal 23

Activity on arc or arrow 1 2 Same example on AON network A,12 Chapter 4 Slides by: Ms. Shree Jaswal 24

Activity Immediate Predecessors Duration A _ 6 B A 9 C A 8 D B,C 4 E B 6 F D,E 6 Duration is in days Chapter 4 Slides by: Ms. Shree Jaswal 25

1 2 Chapter 4 Slides by: Ms. Shree Jaswal 26

Activity Immediate Predecessors Duration A _ 6 B A 9 C A 8 D B,C 4 E B 6 F D,E 6 Duration is in days Chapter 4 Slides by: Ms. Shree Jaswal 27

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Activity Immediate Predecessors Duration A _ 6 B A 9 C A 8 D B,C 4 E B 6 F D,E 6 Duration is in days Chapter 4 Slides by: Ms. Shree Jaswal 29

3 1 2 5 6 4 Chapter 4 Slides by: Ms. Shree Jaswal 30

Activity Immediate Predecessors Duration A _ 6 B A 9 C A 8 D B,C 4 E B 6 F D,E 6 Duration is in days Chapter 4 Slides by: Ms. Shree Jaswal 31

3 7 1 2 5 6 4 Chapter 4 Slides by: Ms. Shree Jaswal 32

Activity Immediate Predecessors Duration A _ 6 B A 9 C A 8 D B,C 4 E B 6 F D,E 6 Duration is in days Chapter 4 Slides by: Ms. Shree Jaswal 33

3 7 8 9 1 2 5 6 4 3-5, 4-5, 7-8,6-8 are dummy activities Chapter 4 Slides by: Ms. Shree Jaswal 34

Dummy activities are used in AOA diagrams in case a node has more than one immediate predecessor. In previous example: Activity Immediate Predecessors Duration D B,C 4 F D,E 6 To represent activities D & F we use dummy activities Chapter 4 Slides by: Ms. Shree Jaswal 35

REDUNDANT ACTIVITY ACTIVITY PREDECESSOR IMMEDIATE PRED: REDUNDANT PRED: A -- B A A C A A D A,B,C B,C A E A,B,C,D D A,B,C F A,B,C B,C A Chapter 4 Slides by: Ms. Shree Jaswal 36

It is only essential to know the immediate predecessor of a node while constructing a network. All the predecessors except the immediate predecessors of a node are redundant predecessors( activities). Chapter 4 Slides by: Ms. Shree Jaswal 37

AON n/ws There are no dummy activities They are simpler They are easier to construct. Chapter 4 Slides by: Ms. Shree Jaswal 38

AOA n/w s AOA method used just as often, probably because it was developed first and is better suited for PERT procedures The PERT model places emphasis on events and in the AOA method events are specifically designated by nodes. AOA diagrams use line segments to represent flow of work and time, it is easy to construct schedules that are similar in appearance to Gantt charts but incorporate advantage of networks Chapter 4 Slides by: Ms. Shree Jaswal 39

Most software packages create AOA n/w s that look similar to Gantt charts. In particular it is best to select one form of technique., AON or AOA, and stick to it. Chapter 4 Slides by: Ms. Shree Jaswal 40

The longest path from the origin node to the terminal node Gives the expected project duration (Te) One project can have more than one CP Shortening activities on CP (critical activities) will help reduce the project duration Shortening activities NOT on CP has no effect on project duration Delay in any activities on CP will result in delay of project completion Chapter 4 Slides by: Ms. Shree Jaswal 41

Activity, duratio n A,6 - B,9 A C,8 A D,4 B,C E,6 B,C predece ssor B,9 D,4 Start A,6 Finish C,8 E,6 Critical path A-B-E:21 weeks Chapter 4 Slides by: Ms. Shree Jaswal 42

Specifies when at the earliest the activities can be performed. ES & EF are computed by taking a FORWARD pass through the network When an activity has several predecessors, its ES is the MAXIMUM of all EF of predecessors Chapter 4 Slides by: Ms. Shree Jaswal 43

Latest allowable times that the activity can be started and finished without delaying the completion of the project. LS & LF are computed by taking a REVERSE pass through the network. LS for the last activity (Ts) is taken same as the EF for that activity (Te); larger value can be selected if project does not have to be completed by EF. When an activity with multiple paths leading back, backward path with MINIMUM of all LS is selected. Chapter 4 Slides by: Ms. Shree Jaswal 44

Eg: activity duration predecessor A requirements analysis 3 weeks - B programming 7 weeks A C get hardware 1 week A D train users 3 weeks B, C Chapter 4 Slides by: Ms. Shree Jaswal 45

3 1 2 5 6 4 Critical path is: A-B-D 13 weeks Chapter 4 Slides by: Ms. Shree Jaswal 46

Total slack= LS-ES or LF-EF Total slack of all activities along critical path is zero. Hence delaying any of these activities will delay the project. Chapter 4 Slides by: Ms. Shree Jaswal 47

Free Slack= ES( earliest successor)- EF In the eg, activity C has a free slack of 6 weeks( 10-4=6) Free slack indicated the amount by which activity can be delayed without affecting the start of its successor activity. Chapter 4 Slides by: Ms. Shree Jaswal 48

can have more than one critical path activity duration predecessor A requirements analysis 3 weeks - B programming 7 weeks A C get hardware 7 weeks A D train users 3 weeks B, C critical paths A-B-D A-C-D both with duration of 13 weeks Chapter 4 Slides by: Ms. Shree Jaswal 49

After a project network has been created and finalized the resulting schedule times should be converted into a calendar schedule plan Calendar schedule plan expresses the schedule in terms of calendar dates Chapter 4 Slides by: Ms. Shree Jaswal 50

To complete the calendar schedule, the network is converted into a time-based network Time based n/w s have advantages of both Gantt charts and networks because they show the calendar schedules as well as relationships among activities. Chapter 4 Slides by: Ms. Shree Jaswal 51

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The Te first computed from the n/w is usually not the duration specified as the contractual completion time. A Management schedule reserve is established by setting the required target time Ts at some amount greater than the time of the final schedule event Te. Chapter 4 Slides by: Ms. Shree Jaswal 55

The schedule reserve and a management budget reserve comprise a safety buffer that the project manager can use to overcome problems or delays that threaten project performance Chapter 4 Slides by: Ms. Shree Jaswal 56

Need for PDM: Predecessor - Sucessor type of networks assume a strict sequential relationship between activities They do not provide for tasks that can be started when their predecessors are only partially complete PDM allows multiple relationships between activities Finish-to-Start (FS) Start-to-Start (SS) Start-to-Finish (SF) Finish-to-Finish (FF) Chapter 4 Slides by: Ms. Shree Jaswal 57

Finish-to-Start (FS) The start of the Activity B can occur n days, at the earliest after the finish of Activity A Start-to-Start (SS) The start of Activity B can occur n days, at the earliest after the start of Activity A Chapter 4 Slides by: Ms. Shree Jaswal 58

Start-to-Finish (SF) The finish of Activity B must occur n days, at the latest after the start of Activity A Finish-to-Finish (FF) The finish of Activity B will occur in n days, at the latest after Activity A finishes Chapter 4 Slides by: Ms. Shree Jaswal 59

PDM: Relationships A 15 Plaster Wall FS=5 B 10 Tear-down scaffolding A 15 Furniture move in SS=5 B 10 People move in A A FS=5 SS=5 B B A 15 Test new system SF=20 B 10 Phase out old system A 15 Lay asphalt FF=5 B 10 Paint parking lines A SF=20 A FF=5 B B Chapter 4 Slides by: Ms. Shree Jaswal 60

The two most commonly used methods for project planning and scheduling are: Program Evaluation and Review Technique (PERT) Critical Path method (CPM) Chapter 4 Slides by: Ms. Shree Jaswal 61

Program Evaluation & Review Technique (PERT) The Framework for PERT and CPM There are six steps which are common to both 1. Define the Project and all of it s significant activities or tasks. 2. Develop the relationships among the activities. Decide which activities must precede and which must follow others. Chapter 4 Slides by: Ms. Shree Jaswal 62

3. Draw the "Network" connecting all the activities. Each Activity should have unique event numbers. Dummy arrows are used where required to avoid giving the same numbering to two activities 4.Assign time and/or cost estimates to each activity 5. Compute the longest time path through the network. This is called the critical path. 6.Use the Network to help plan, schedule, monitor and control the project. Chapter 4 Slides by: Ms. Shree Jaswal 63

PERT was developed for application in projects where there is uncertainty associated with the duration and nature of activities. Chapter 4 Slides by: Ms. Shree Jaswal 64

reflects PROBABILISTIC nature of durations assumes BETA distribution same as CPM except THREE duration estimates optimistic most likely pessimistic Chapter 4 Slides by: Ms. Shree Jaswal 65

Three time estimates : The Optimistic (a) The minimum time in which the activity can be completed The Most Likely (m) Completion time having the highest probability (normal time to complete the job) The Pessimistic (b) The longest time an activity could take to complete Chapter 4 Slides by: Ms. Shree Jaswal 66

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a = optimistic duration estimate m = most likely duration estimate b = pessimistic duration estimate Mean or expected time for completion of an activity, te is given by te = (a + 4m + b)/6 Variance, V is given by V = sqr((b-a)/6) Chapter 4 Slides by: Ms. Shree Jaswal 68

The expected time Te, represents the point on distribution where there is a 50-50 chance that the activity will be completed earlier or later than it. a=3,b=5,c=13 Te= (3+4(5)+13)/6= 6 days Variance is the measure of variability in the activity completion time: V=sqr((13-3)/6)=sqr(1.67)= 2.78 Chapter 4 Slides by: Ms. Shree Jaswal 69

The larger V, the less reliable Te, and the higher the likelihood that the activity will be completed much earlier or much later than Te. More dispersed the distribution and greater the chance that the actual time will be significantly different from the expected time Te Chapter 4 Slides by: Ms. Shree Jaswal 70

Probability of finishing by a target completion date The expected duration of a project - Te, is the sum of expected activity times along the critical path. Te = te The variation in the project duration distribution is computed as the sum of the variances of the activity durations along the critical path Vp = V Chapter 4 Slides by: Ms. Shree Jaswal 71

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Now, although the project is estimated to be completed within 29 weeks (T e =29) our Project Director would like to know what is the probability that the project might be completed within 27 weeks (i.e.ts=27 or Due Date or D=27). For this calculation, we use the formula for calculating Z, the number of standard deviations that D is away from T e. Z =(Ts-Te)/ Vp Chapter 4 Slides by: Ms. Shree Jaswal 73

Thus, Z=(27-29)/ 6 = -0.82 After referring to table for Z values for normal distribution, X1=-0.8,X2=-1.0,Y1=0.212,Y2=0.159 Now, using the formula, Y=Y1+[(Y1-Y2)/X1-X2)]*(X-X1), we get Y=0.2067=0.21(approx) Therefore, probability is 21% to finish project in 27 days Chapter 4 Slides by: Ms. Shree Jaswal 74

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For above example to find out what is the date when 95% of project will have been completed.. Again using the table and interpolating, probability of 0.95 has Z value=1.645 Thus,1.645=(Ts-29)/ 6 So, Ts=33.03 days (highly likely) Chapter 4 Slides by: Ms. Shree Jaswal 76

Putting too much emphasis on the critical path can lead managers to ignore other paths that are near-critical or have large variances, and which themselves could easily become critical Chapter 4 Slides by: Ms. Shree Jaswal 77

Monte Carlo simulation is a procedure that takes into account the effects of near critical paths becoming critical. Chapter 4 Slides by: Ms. Shree Jaswal 78

Need to have considerable amount of historical data to make time estimates PERT gives overly optimistic results. Beta distribution gives large errors in estimating Te. Most of the errors in Te come from faulty time estimates not Beta distribution. Chapter 4 Slides by: Ms. Shree Jaswal 79

Although PERT and CPM employ networks and use the concept of critical path, the methods have two points of divergence. CPM is a deterministic approach. CPM includes a mathematical procedure for estimating the trade-off between project duration and cost. CPM features analysis of reallocation of resources from one job to another to achieve the greatest reduction in project duration for the least cost. Chapter 4 Slides by: Ms. Shree Jaswal 80

Meaning BASIS FOR COMPARISON PERT PERT is a project management technique, used to manage uncertain activities of a project. CPM CPM is a statistical technique of project management that manages well defined activities of a project. What is it? A technique of planning and control of time. A method to control cost and time. Orientation Event-oriented Activity-oriented Evolution Evolved as Research & Development project Evolved as Construction project Chapter 4 Slides by: Ms. Shree Jaswal 81

BASIS FOR COMPARISON PERT CPM Model Probabilistic Model Deterministic Model Focuses on Time Time-cost trade-off Estimates Three time estimates One time estimate Appropriate for Critical and Noncritical activities Suitable for High precision time estimate No differentiation Research and Development Project Reasonable time estimate Differentiated Non-research projects like civil construction, ship building etc. Crashing concept Not Applicable Applicable Chapter 4 Slides by: Ms. Shree Jaswal 82

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Tn- how long the activity will take under normal work conditions. Also associated with normal pace is the normal cost, Cn, the price of doing the activity in normal time. Usually normal pace is assumed to be the most efficient and thus least costly pace. When maximum effort is applied, the duration so that activity can be completed in the shortest possible time, the activity is said to be crashed. Chapter 4 Slides by: Ms. Shree Jaswal 84

In our example, cost slope for the activity is $3K per week. Thus, for each week the activity duration is reduced( sped up) from the normal time of 8 weeks, the additional cost will be $3K. Completing the project 1 week earlier i.e. 7 weeks, would increase the project cost by ($9K +$3K=$12K) Chapter 4 Slides by: Ms. Shree Jaswal 85

Basic rules: Reducing the duration of an activity, increases the cost by the cost-slope. Increasing the cost of activity, reduces the duration of the activity Reduce the duration of activity with min value of cost slope. Chapter 4 Slides by: Ms. Shree Jaswal 86

Activity Normal Crash Cost Slope Tn Cn Tc Cc A 9 10 6 16 2 B 8 9 5 18 3 C 5 7 4 8 1 D 8 9 6 19 5 E 7 7 3 15 2 F 5 5 5 5 _ G 5 8 2 23 5 $55K $104K Chapter 4 Slides by: Ms. Shree Jaswal 87

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Activity Normal Crush Cost Slope Tn Cn Tc Cc A 9 10 6 16 2 B 8 9 5 18 3 C 5 7 4 8 1 D 8 9 6 19 5 E 7 7 3 15 2 F 5 5 5 5 _ G 5 8 2 23 5 $55K $104K Chapter 4 Slides by: Ms. Shree Jaswal 89

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Observe that activities are plotted using values of Tc

CCPM was introduced in 1997 by Eliyahu Goldratt. CCPM is based on the idea that people often inflate or add cushioning to their time estimate in order to give themselves a form of safety to compensate for uncertainty. There are 3 basic reasons for inflating: If your work is dependent upon the work of someone else Because of pessimism arising from a previous experience where things did not go as planned To guard against the cut which the project sponsor or customer may put Chapter 4 Slides by: Ms. Shree Jaswal 95

Added safety does not ensure timely completion of projects due to following reasons: 1. Student s syndrome 2. Parkinson s law 3. Resource contention Chapter 4 Slides by: Ms. Shree Jaswal 96

CCPM follows a completely different assumption: instead of adding safety to each task, put that safety in the form of buffers where needed the most. This would be in the form of feeding buffers, resource buffers & a buffer at the end of the project CCPM begins by asking each person or team assigned to a task to provide an estimate that would have a 50 % chance of being completed Critical chain is different from the critical path in that it also takes into account resource contention. Chapter 4 Slides by: Ms. Shree Jaswal 97

Project schedule with safety in each task A,10 B,10 C,10 E,10 D,10 Critical Path: A-B-C-E, duration 40 days Critical chain project schedule A,5 B,5 C,5 E,5 10 D,5 2.5 Buffer Feeder buffer Chapter 4 Slides by: Ms. Shree Jaswal 98

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In earlier slides, it was assumed that the resources are available (may be at a cost) in abundance In reality, some resources may be scarce or shared Resource loading refers to the amount of resource required to conduct a project Note: resource loading keeps changing throughout a project because the amount of resources needed for individual activities differs Chapter 4 Slides by: Ms. Shree Jaswal 102

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Resource leveling refers to scheduling activities in a manner such that the resource loading is somewhat balanced (or smoothed ) SMOOTHING: flatten as much as possible Smoothed: Manpower Chapter 4 Slides by: Ms. Shree Jaswal 104

Equipment Requirement(!Erratic!) Chapter 4 Slides by: Ms. Shree Jaswal 105

LEVELING: flatten with reference to available resource Leveled: Manpower Chapter 4 Slides by: Ms. Shree Jaswal 106

Activities must be scheduled so that the allocation of a particular resource to project activities does not exceed a specified maximum Attention is given to maximum availability of resource Most project management scheduling software use heuristics (procedure based upon a simple rule) for making the decisions The heuristic rule for determining the scheduling priority are: Chapter 4 Slides by: Ms. Shree Jaswal 107

A E B C D F 5 5 10 10 5 5 The critical path length is 9 weeks and the constrained-resource level is of 10 workers Chapter 4 Slides by: Ms. Shree Jaswal 108

a. As soon as possible: activities that can be started sooner are given priority over those that must be started later 10 5 B A C D E F As Soon As Possible 11 Chapter 4 Slides by: Ms. Shree Jaswal 109

b. As late as possible: activities that can be finished later are given lower priority than those that must be finished earlier 10 5 B D C A F E As Late As Possible 10 Chapter 4 Slides by: Ms. Shree Jaswal 110

c. Most resources : activities requiring more resources are given priority over those requiring fewer resources 10 5 B A C D E F Most Resources 11 Chapter 4 Slides by: Ms. Shree Jaswal 111

d. Shortest Task Time: activities of shorter duration are given priority over those of longer duration 10 B E 5 D C A F Shortest Task First 11 Chapter 4 Slides by: Ms. Shree Jaswal 112

e. Least Slack: activities with less slack time are given priority over those with more slack time (critical path activities are given highest priority) 10 5 B A C E F D Least Slack time 11 Chapter 4 Slides by: Ms. Shree Jaswal 113

All these rules are subordinate to precedence requirements, which means whatever the rule, the resulting schedule will not violate the necessary predecessor-successor relationship. Other ways to account for resource constraints in project scheduling include: Reduce the level of resources per activity Split activities Alter the network: use PDM, convert FS to SS relationships Chapter 4 Slides by: Ms. Shree Jaswal 114