Slide 8.1 4E1 Project Management Network Representation and Critical Path Analysis - Part 1.
Slide 7.1 4E1 Project Management Planning 2 Estimating and Scheduling.
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Transcript of Slide 7.1 4E1 Project Management Planning 2 Estimating and Scheduling.
Slide 7.1
4E1 Project Management
Planning 2 Estimating and Scheduling
Slide 7.2
Key Concepts
Estimating
Scheduling
Gantt charts
Network notations
Slide 7.3
Exercise
Take a blank sheet of paper• Divide it into five columns as follows:
# Best guess Upper estimate Lower estimate
1 2 3 .. 10
There should be ten rows to write on.
Slide 7.4
Test Your General KnowledgeFor each item, write (a) best guess and (b) upper and lower estimates that you are 90% confident of.
1. Distance in miles from Moscow to Santiago (in Chile)
2. Gold medals won by Finland in summer Olympics 1896-1992
3. Area of Greenland in square miles
4. Year the ballpoint pen was invented
5. Year the HJ Heinz company was founded
6. Population of Belize in 1990
7. Denmark’s GNP in $US in 1989
8. Year that Louis Braille was born
9. Average depth of Pacific ocean to nearest 1,000 feet
10. Length in miles of the river Danube
Slide 7.5
Answers
1. Distance from Moscow to Santiago is 10,118 miles2. Finland won 97 gold medals in summer Olympics 1896-
19923. The area of Greenland is 839,781 square miles4. The ballpoint pen was invented in 19385. The HJ Heinz company was founded in 18766. The population of Belize in 1990 was 187,0007. Denmark’s GNP in $US in 1989 was $105,238 million8. Louis Braille was born in 18099. The Pacific ocean is 14,000 feet deep on average10. The river Danube is 1,770 miles long
Slide 7.6
Why are Estimates So Often Wrong?
Internal causes• Psychology: over-confidence, optimism, ego
• Misjudgement: inexperience, uniqueness of project
• Failure to learn from previous projects
External pressures• Management pressure, sales imperative
Other causes• Games, inadequate specifications, unclear objectives
• Rarely, bad luck
Slide 7.7
Example: Software Estimating How many steps in this C program to convert Fahrenheit to Celsius?
#define LOWER 0#define UPPER 300#define STEP 20main()
{int fahr for (fahr=LOWER
fahr<=UPPER fahr=fahr+STEP)
print(“%4d %6.1f\n”,fahr,(5.0/9.0*(fahr-32))}
Slide 7.8
Experts’ Estimates
0
2
4
6
8
10
12
One Two Three Four Five Six Seven Eight Nine
No. of Experts
Slide 7.9
Estimating – Broad StrategiesBases
• Experience, similar work in previous projects• Detailed breakdown/WBS• Heuristics e.g. function points
Types• Ballpark, comparative, feasibility, detailed• Top-down vs bottom-up
Risks• Theoretical versus actual resource costs• Cumulative effect of small errors
Slide 7.10
Scheduling: Context
StatutoryRegulations
Acts of God
Market Conditions
CorporateStrategy
FiscalPolicy
Organisationstructure
Proceduresand systems
Communications
Resourcesand capacity
Attitudes and culture
Technicalcapability
SupportingServices
Managementskills
ProfitTimeQuality
External Factors
Working factors
Contribution to results
Planningand
Scheduling
Slide 7.11
The Bar (Gantt) Chart
Design
Set up
Manufacture
Test
Task
Time
Purchasematerials
Implicit dependency
Overlap
Henry Gantt
Lag
Explicit dependency
Slide 7.12
Gantt Charts in Practice
Slide 7.13
ExerciseDraw a Gantt chart for your “Gulliver Experience” project, showing only the top-level tasks (i.e. about 7 phases)
• Planning Project plan, agree requirements
• Outsource project Issue request for tenders, review proposals, award contract
• Design Architectural design, detailed design and blueprints, order materials
• Move TCD administration Prepare new location, move
• Construction Site preparation, building, fit-out
• Set up business Establish company, hire staff, implement systems, marketing
• Commence business operations
Add estimated durations, start and end dates, dependencies and resources
Slide 7.14
Network Diagrams
1
84
36
9
7
52
1 432Get up Eat breakfast Go to college
10 20 30
Activity on arrow
Slide 7.15
Activity Properties
Description
Resources: human, other
Work/non-work
Duration
Dates: earliest start, latest finish
Dependencies: predecessors, successors
Other constraints
Slide 7.16
Precedence
1
84
36
9
7
521
3 5
24
4
3
4
55
18
6
Dummy task (dashed line) indicates order• Node 4 precedes node 5
• Therefore tasks 5 and 8 cannot start until task 3 is complete
Slide 7.17
Types of Network Diagram
Two basic types:
Activity on arrow (most intuitive)• Arrow diagrams (ADM)
• Critical Path Method (CPM)
• Critical Path Analysis (CPA)
• Project Evaluation and Review Technique (PERT)
Activity on node (suits computers)• Precedence diagrams (PDM)
• Rare but still used Method of potentials (MPM)
Activities on circular nodes
Slide 7.18
Precedence Diagrams
Get up10
Eat breakfast20
Go to college30
Slide 7.19
Precedence Diagrams - Dummy Tasks
Not customary but can be useful
Slide 7.20
Exercise
A
B
D
C
F
W
G
E
V
X
Y
Z
Activity AF
Activity BE
Activity CE
Activity DE
Activity FV
Activity FW
Activity FX
Activity GY
Activity GZ
Redraw this arrow diagram as a PDM (a) with dummy tasks and (b) without dummy tasks
Slide 7.21
Solution (without dummy tasks)
CE
AF
DE GY
FX
FV
BE FW
GZ
Slide 7.22
Solution (with dummy tasks)
CE
AF
DE GY
FX
FV
BE FW
GZ
Dummy 2
Dummy 1
Slide 7.23
Network Notations - Example 1
Screed Floor
D =26 Bus = 35ES = 2/10 LS = 15/10 EC = 6/11 LC = 23/11Res = FEB, JH
Duration
ActivityDescription
Earliest Start Date
Earliest CompletionDate
ResourcesAssigned
LatestCompletionDate
LatestStart Date
Elapsed time
B1.3
Activity Code
Networks use standard notation as follows:
Slide 7.24
Activity identifier
Earliest event time
Latestevent time
1025
17
5 10 15
8 3 18
Earliest start time
DurationEarliest finish
time
Latest start time
Total float Latest finishtime
Activity identifier and descriptionResources required.
Network Notations - Example 2
Slide 7.25
14/11/06 5 15/12/06 4.2.3 Specify Hardware3/12/06 17 18/1/05JO’D €2,500 0%
Earliest Start Time Duration
Earliest Finish Time
Latest Start Time
Latest Finish Time
Total Float
Resources/Responsibility
Budget% Complete
Task ID
Task Description
Network Notations - Example 3
Slide 7.26
Gantt vs Network
Both used widely
Gantt• Simpler, easier to grasp
• Limited in ability to show dependencies
• Easily cluttered
Networks• More meaningful, more information
• Harder to read
• Often large and complex
Slide 7.27
Summary: Key Points
Estimating• Part science, part art
• Tools help but judgment is required
Gantt charts• Most basic tool; intuitive but limited
Network (arrow/precedence) diagrams• More powerful, less intuitive