Critical path analysis 3.3.4

Question 1

What is critical path analysis?

Answer 1

Is a project analysis and planning method that allows a project to be completed in the shortest possible time.

Question 2

What is a critical path?

Answer 2

The sequence of project activities adds up to the longest overall duration. The critical part of the time is the shortest possible time to complete the project.

Question 3

Why do businesses need to plan complex projects?

Answer 3

• Many large businesses get involved in projects that are complex and have significant investment risk.
• As the complexity and risk increase it becomes even more necessary to identify the relationship between the activities involved and work at the most efficient way of completing the project.

Question 4

What is the information needed for CPA?

Answer 4

• A list of all activities required to complete the project.
• The time (duration) that each activity will take to complete.
• The dependencies between the activities (e.g. activity D cannot come be completed until activities B and C are done).

Question 5

What does the CPA diagram calculate?

Answer 5

• The longest path of planned activities to the end of the project (critical path)
• The earliest start time (EST) and latest finishing time (LFT) that each activity can start and finish without making the project longer.
• Which activities are critical (i.e. on the longest path) and which have float (i.e. can be delayed without making the project longer)

Question 6

What part of the node is the EST?

What part of the node is the LFT?

What part of the node is the node ref?

What part of the CPA diagram is the activity?

What part of the CPA diagram is the duration?

Answer 6

Top right

Bottom right

Left half section

Top of the line at the same level as the EST.

The bottom half of the line is at the same level as the LFT.

Question 7

What are the 4 golden rules of a CPA diagram?

Answer 7

• EST – Calculate first and always work from left to right.
• EST – Where two or more activities meet, EST is always the highest calculated figure.
• LFT – Calculate after EST and always work from right to left.
• LFT – Where two or more activities meet, LFT is always the lowest calculated figure.

Question 8

How do you calculate the float time?

Answer 8

The float time is the duration an activity can be extended or delayed so that the project still finishes within the minimum time.

Calculated as:

LFT- EFT

Question 9

How do you calculate the LFT?

Answer 9

• Give the last node of the project an LFT= The last EST.
• Work backwards from right to left.
• Subtract the duration of the activity from the LFT.

Question 10

How do you identify the critical path?

Answer 10

Activities with a float of 0 cannot be delayed without delaying the entire project. Such activities represent the critical path. On the critical path, activities are equal EST and an LFT and zero float.

Question 11

What are the uses of critical path analysis?

Answer 11

• Estimate to minimise project time. Support project costing and evaluation.
• Plan and organise resources (move from activities with float).
• Prioritise tasks.

Question 12

Why is CPA so important?

Answer 12

Any delay activity in the critical path directly impacts of planned project completion date.

Question 13

What are the advantages of CPA?

Answer 13

• Most importantly – helps reduce the risk and costs of complex projects.
• Encourages careful assessment of the requirements of each activity in a project.
• Help spot which activities have some slack (“float”) and could therefore transfer some resources = better allocation of resources.
• A decision-making tool and a planning tool – all in one!
• Provides managers with a useful overview of a complex project.
• Links well with other aspects of business planning, including cash flow forecasting and budgeting

Question 14

What are the disadvantages of CPA?

Answer 14

• Reliability of CPA is largely based on accurate estimates and assumptions made.
• CPA does not guarantee the success of a project – that still needs to be managed properly.
• Resources may not actually be as flexible as management hope when they come to addressing the network float.
• Too many activities may the network diagram too complicated. Activities might themselves have to be broken down into mini-projects.