Critical Path Analysis in Project Management

Question 1

What is the purpose of project scheduling?

Answer 1

• Comprehensive and comprehensible picture of project activities
• Illustrates relationships between activities
• Communicates plan to others
• Tends to be graphical
• Key means of estimating and controlling the project

Question 2

What are Gantt charts?

Answer 2

• Developed in early 20th century
• Give a clear, pictorial model of the project
• Are simple and require very little training to understand and use
• Show progress
• Can be used for resource planning
• Can show inter-relationships and critical path

Question 3

What are the advantages of Gantt charts?

Answer 3

• Simple to draw and read
• Good in static environments
• Useful as an overview
• Very widely used
• Graphical interface of most PC project planning systems (e.g. MS Project)

Question 4

What are the disadvantages of Gantt charts?

Answer 4

• Difficult to update manually
• Can become obsolete (and discredited)
• Does not equate time with cost
• Does not help in optimising resources

Question 5

What is Project network analysis?

Answer 5

• Shows the activities, the logical sequence and interdependencies, and the total time required to complete a project
• Handles inter-relationships between activities
• Identifies activities critical to the project finishing on time
• Take time to produce but valuable for all but the smallest of projects

Question 6

What is the activity?

Answer 6

Task or set of tasks required to deliver the project

Question 7

What is the event?

Answer 7

Identifiable state resulting from completion of one or more activities

Question 8

What is a milestone?

Answer 8

Identifiable and noteworthy events, marking significant progress

Question 9

What is a network?

Answer 9

A diagram of nodes and directional arcs that define the project and illustrate relationships between activities

Question 10

What is a path?

Answer 10

A series of connected activities between any two events

Question 11

What is a critical path?

Answer 11

The set of activities on a path from the project’s start event to the finish event that, if delayed, will delay the completion of the project

Question 12

What is a critical event?

Answer 12

The time required to complete all activities on critical path

Question 13

How do you build a network?

Answer 13

Activity on Node (AON) Network

Activity A dependency Activity B

Question 14

What are the basic rules for networks?

Answer 14

• Networks flow from left to right
• An activity cannot begin until ALL preceding connected activities have been completed
• Arrows indicate precedence and flow, and can cross over each other
• Each activity should have a unique identification number (use WBS)
• LOOPING is not allowed
• CONDITIONAL STATEMENTS are not allowed
• It is good practice to use a single ‘Start’ node and a single ‘Finish’ node

Question 15

What is the CPA analysis?

Answer 15

• Earliest Start Time (ES)
• Earliest Finish Time (EF)
• Latest Start Time (LS)
• Latest Finish Time (LF)
• Duration (d)
• Total Float or Slack (TF)
• Forward Pass
• Reverse / Backward pass
• Critical patch

Question 16

What are the advantages of AON?

Answer 16

• No dummy activities are used
• Events not used, just activities
• AON easy to draw when dependencies and relationships are straightforward
• Activity emphasis easily understood by all levels in the organisation

Question 17

What are the disadvantages of AON?

Answer 17

• Path tracing by activity number can be difficult to envisage - little sense of flow
• Network drawing and understanding difficult when dependencies are numerous and complex

Question 18

What are the two types of errors in predicting the future?

Answer 18

Random errors = the chances and sizes of over and under-estimates are about equal, these ‘balance’ out when summed

Biased or systematic errors = the chance and size of under and over-estimates are not equal, these errors do not cancel out when summed