The purpose and process of network analysis

Network analysis is a planning tool used to organise resources and activities for completing complex projects in the most time-efficient and cost-effective manner. It is also known as critical path analysis and helps businesses implement strategies by identifying the quickest way to finish a project.

Steps in the process of network analysis

1. Identify all activities involved in the project and determine their sequence or order.
2. Estimate the duration of each activity.
3. Arrange the activities into a network diagram that shows the entire project, including which tasks can be performed at the same time.
4. Identify the shortest time required to complete the project overall.

Key components including nodes, critical path, and time calculations

Network diagrams use specific elements to map out projects, highlighting dependencies and timelines. These components help determine the minimum project duration and identify tasks that cannot be delayed.

Nodes in network diagrams

Nodes are circles in the diagram that mark the end of one activity and the start of another.

Each node is divided into three parts:

• The node number.
• The earliest start time (EST) for the next activity.
• The latest finishing time (LFT) for the previous activity.

The critical path and critical activities

The critical path is the sequence of tasks that must be completed one after another without any delays to finish the project in the shortest possible time. Critical activities are those on this path; any delay in these will extend the entire project duration.

Time calculations in network analysis

Several calculations are used to determine timings within the network.

Calculating earliest start time (EST)

The EST is the earliest time an activity can begin, based on the completion of previous activities.

$\text{EST}=\text{EST of previous activity}+\text{duration of previous activity}$

Where:

• EST of previous activity = Earliest start time of the task before the current one
• Duration of previous activity = Time taken to complete the task before the current one

Calculating earliest finishing time (EFT)

The EFT is when an activity will end if started at its EST.

$\text{EFT}=\text{EST}+\text{duration}$

Where:

• EST = Earliest start time of the activity
• Duration = Time taken to complete the activity

Calculating latest finishing time (LFT)

The LFT is the latest time an activity can finish without delaying the project. It is calculated by working backwards from the final node's completion time.

$\text{LFT}=\text{LFT of next activity}-\text{duration of next activity}$

Where:

• LFT of next activity = Latest finishing time of the task after the current one
• Duration of next activity = Time taken to complete the task after the current one

Calculating latest start time (LST)

The LST is the latest time an activity can start while still finishing by its LFT.

$\text{LST}=\text{LFT}-\text{duration}$

Where:

• LFT = Latest finishing time of the activity
• Duration = Time taken to complete the activity

Worked example - Calculating EST, EFT, LFT, and LST in a network

A project has three activities: A (duration 5 days), B (duration 4 days, dependent on A), and C (duration 3 days, dependent on B). The project must be completed by day 15. Calculate the EST, EFT, LFT, and LST for activity B, assuming activity A starts at day 0.

Step 1: Identify the values

• Duration of A = 5 days
• Duration of B = 4 days
• Duration of C = 3 days
• Project end = Day 15
• EST of A = 0

Step 2: Calculate EST and EFT for B

$\text{EST of B}=\text{EST of A}+\text{duration of A}=0+5=5$ $\text{EFT of B}=\text{EST of B}+\text{duration of B}=5+4=9$

Step 3: Calculate LFT and LST for B (working backwards)

$\text{LFT of C}=15$ $\text{LFT of B}=\text{LFT of C}-\text{duration of C}=15-3=12$ $\text{LST of B}=\text{LFT of B}-\text{duration of B}=12-4=8$

Step 4: Interpretation

Activity B can start as early as day 5 and must finish by day 12 to avoid delaying the project.

Float time and dummy activities

Float time and dummy activities help manage flexibility and dependencies in network diagrams, ensuring accurate representation of project constraints.

Float time in network analysis

Float time is the spare time available for non-critical activities, allowing them to be delayed without affecting the overall project completion. Total float is the maximum delay possible for an activity.

$\text{Total float}=\text{LFT}-\text{duration}-\text{EST}$

Where:

• LFT = Latest finishing time of the activity
• Duration = Time taken to complete the activity
• EST = Earliest start time of the activity

Activities on the critical path have zero float.

Dummy activities in network diagrams

Dummy activities are imaginary tasks shown as dashed lines in the diagram. They indicate dependencies between activities without adding time or resources, ensuring the network accurately reflects which tasks must precede others.

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Worked example - Calculating total float

In a project, an activity has an EST of 6 days, a duration of 3 days, and an LFT of 11 days. Calculate the total float.

Step 1: Identify the values

• EST = 6 days
• Duration = 3 days
• LFT = 11 days

Step 2: Apply the total float formula

$\text{Total float}=11-3-6=2\text{ days}$

Step 3: Interpretation

This activity can be delayed by up to 2 days without impacting the project's overall timeline.

Applications, advantages, and disadvantages of network analysis

Network analysis has various practical uses in business and project management, along with benefits and limitations.

Applications of network analysis

• Implementing business strategies or planning complex projects.
• Determining when resources, such as materials or staff, need to be available.
• Identifying ways to shorten the critical path by adding resources.
• Allocating and optimising resources across tasks.
• Supporting decision-making based on project timelines.

Advantages of network analysis

• Identifies critical activities that need close monitoring.
• Allows resources to be shifted from activities with float time to critical ones.
• Enables different project functions to begin at the earliest possible time.
• Assists in forecasting cash flow needs based on activity timings.
• Determines the shortest possible time to complete the project.
• Provides a visual aid for communicating the project plan.
• Encourages systematic planning of activities and dependencies.
• Facilitates monitoring of progress on individual tasks.
• Can be updated as the project evolves.

Disadvantages of network analysis

• Depends on time estimates that may be unreliable or inaccurate.
• Requires considerable time and effort to create the network diagram.
• Imposes tight deadlines that could encourage shortcuts and reduce quality.
• Focuses on time but does not consider costs or overall project quality.