Forward and backward pass in ms project

MGT400 – Project Management Chapter 6: Developing a Project Plan

Where are we now?

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Lecture Content • Developing a Project Plan:

• What is Gantt Chart? • Example of Gantt Charts.

• What is Project Network? • Link between Project Network and WBS. • Example 1: Building Intranet Application.

• Terminologies of Project Network • Network Activities Data boxes • Network Computation Process • Determinate Project Duration • Example 2: Painting Project

• Forward Pass Calculations

• Backward Pass Calculations.

• Precedence Relationships: • Finish to Start • Start to Start • Finish to Finish • Start to Finish.

• Duration Estimation

• Example 3: Research Project • Determining Critical Path • Review of Forward/Backward Pass • Identify Free Slack (Float)

• Laddering Activities

• Hammock Activities 3

Developing Project Plan

• What is Gantt Chart? • A Gantt chart is a type of bar chart that illustrates a project schedule.

• The bar in each row identifies the corresponding task

• The horizontal position of the bar identifies start and end times of the task

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Gantt Chart using MS Project

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• What is Gantt Chart? – A Gantt chart is a type of bar chart that illustrates a project schedule. – The bar in each row identifies the corresponding task – The horizontal position of the bar identifies start and end times of the task – Bar length represents the duration of the task – Good for allocating resources and re-scheduling – Task durations can be compared easily.

Developing a Project Plan

•What is Project Network? • “…is a tool used for planning, scheduling, and monitoring project progress” (p.161)

• Similar to Gantt charts:

• Provides an estimate of the project’s duration. Help managers get and stay on plan.

• Provides the basis for scheduling labor and equipment.

• Enhances communication among project participants.

• Highlights activities that are “critical” and can not be delayed.

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Merge/Burst Activities

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Activity A

Activity B

Activity C

Activity D Activity C

Activity B

Activity A

Activity D

Terminologies in Project Network

• Path: a sequence of connected, dependent activities.

• Critical path:

• the longest path through the activity network that allows for the completion of all project-related activities;

• the shortest expected time in which the entire project can be completed.

• Delays on the critical path will delay completion of the entire project

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Network Activity Examples 1

Network Activity Examples 2

Network Activity Data Boxes

Suggested display of key data

Network Activity Data Boxes

Suggested display of key data

SL Slack/Float

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Be prepared as it is going to get complex soon!

Network Activity Data Boxes

Network Computation Process

• Forward Pass—Earliest Times

• How soon can the activity start? (early start—ES)

• How soon can the activity finish? (early finish—EF)

• How soon can the project finish? (expected time—ET)

• Backward Pass—Latest Times

• How late can the activity start? (late start—LS)

• How late can the activity finish? (late finish—LF)

• Which activities represent the critical path?

• How long can activity be delayed? (slack or float—SL)

6–15

Forward Pass Calculations

• Forward Pass

 Starting at the beginning (left) of the network develop early start and early finish dates for each task, progressing to end (right- most box) of the network

• Early Start Date (ES)

 Earliest possible point in time an activity can start, based on the network logic and any schedule constraints

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Early Finish Date (EF)  Earliest possible time the

activity can finish

Duration (DU)  Number of work periods,

excluding holidays or other

nonworking

periods, required to complete

the activity; expressed as

workdays

or workweeks

Task Identification Forward Pass

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Name Duration ES EF

Prep 2

Paint Trim 2

Paint Ceiling 3

Paint Walls 4

Paint Walls (2nd Coat) 2

Clean-up 2

Office repainting Project

Forward Pass Calculation

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Prep #1

2

Paint Trim #2

2

Paint Ceiling #3

3

Paint Walls #4

4

Paint Wall 2 #5

2

Clean up #6

2

Step 1: showing Activities, dependencies, and Durations

SL

Forward Pass Calculation

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Prep #10

2

Paint Trim #22

2

Paint Ceiling #32

3

Paint Walls #42

4

Paint Wall 2 #56

2

Clean up #68

2

Step 2: showing Earliest Start= Predecessor (Earliest Start+ Duration)

SL

Forward Pass Calculation

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Prep #10 2

2

Paint Trim #22 4

2

Paint Ceiling #32 5

3

Paint Walls #42 6

4

Paint Wall 2 #56 8

2

Clean up #68 10

2

Step 3: showing Earliest Finish = Processor Duration + Activity Duration.

SL

Task Identification Forward Pass

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Name Duration ES EF

Prep 2 0 2

Paint Trim 2 2 4

Paint Ceiling 3 2 5

Paint Walls 4 2 6

Paint Walls (2nd Coat) 2 6 8

Clean-up 2 8 10

Office repainting Project

Backward Pass Calculations

• Backward Pass  Calculate late start and late finish dates by starting at project

completion, using finish times and working backwards

• Late Start Date (LS)  Latest point in time that an activity may begin without delaying that

activity’s successor  If the activity is on the critical path, the project end date will be

affected

• Late Finish (LF)  Latest point in time a task may be completed without delaying that

activity’s successor  If the activity is on the critical path, the project end date will be

affected

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Backward Pass Calculation

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Prep #11 2

2

Paint Trim #22 4

2

Paint Ceiling #32 5

3

Paint Walls #42 6

4

Paint Wall 2 #56 8

2

Clean up #68 10

2 10

Step 1: For last activity, establish Latest Finish as equal to Earliest Finish.

SL

Backward Pass Calculation

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Clean up #68 10

2 10

Step 2: For all the other activities: Latest Finish as equal to Earliest Start of the next activity.

Paint Trim #22 4

2 8

Paint Ceiling #32 5

3 8

Paint Wall 2 #56 8

2 8

Paint Walls #42 6

4 6

Prep #10 2

2 2

SL

Backward Pass Calculation

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Step 3: The Latest Start = Latest Finish – Duration

Clean up #68 10

2 108

Paint Trim #22 4

2 86

Paint Ceiling #32 5

3 85

Paint Walls #42 6

4 62

Paint Wall 2 #56 8

2 86

Prep #10 2

2 20

SL

Backward Pass Calculation

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Step 4: The Float/Slack= Earliest Start – Latest Start

Clean up #68 10

2 108

Paint Trim #22 4

2 86

Paint Ceiling #32 5

3 85

Paint Walls #42 6

4 62

Paint Wall 2 #56 8

2 86

Prep #10 2

2 20 0

4

3

00

0

SL

Backward Pass Calculation

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Step 5: The Critical Path are the sequence of activates with Zero Float/slack

Clean up #68 10

2 108

Paint Trim #22 4

2 86

Paint Ceiling #32 5

3 85

Paint Walls #42 6

4 62

Paint Wall 2 #56 8

2 86

Prep #10 2

2 20 0

4

3

00

0

SL

Backward Pass Calculation

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Clean up #68 10

2 108

Paint Trim #22 4

2 86

Paint Ceiling #32 5

3 85

Paint Walls #42 6

4 62

Prep #10 2

2 20 0

4

3

0

0

Paint Wall 2 #56 8

2 86

0

Step 5: The Critical Path are the sequence of activates with Zero Float/slack

SL

Task Identification Forward and Backward Passes

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Name Duration ES EF LS LF Float

Prep 2 0 2 0 2 0

Paint Trim 2 2 4 6 8 4

Paint Ceiling 3 2 5 5 8 3

Paint Walls 4 2 6 2 6 0

Paint Walls (2nd Coat) 2 6 8 6 8 0

Clean-up 2 8 10 8 10 0

Float = Slack (same meaning)

Summary: Task Dependency Types

IT Project Management, Third Edition Chapter 6 30

Laddering Activities

• 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.

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A(3) B(6) C(9) ABC=18 days

Laddered ABC=12 days

A1(1) A2(1) A3(1)

B1(2) B2(2) B3(2)

C1(3) C2(3) C3(3)

Hammock Activities

Used as a summary for subsets of activities

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0 A 5

0 5 5

5 B 15

5 10 15

15 C 18

15 3 18

0 Hammock 18

0 18 18

Useful with a complex project or one that has a shared budget