Effort Slippage

Overview

Effort slippage occurs when the actual effort required to complete a task, milestone, or project exceeds the estimated effort. This metric is also known as Effort Variance.

Effort Slippage Formula

The mathematical formula to compute the metric is as follows:

Effort Slippage =

 

(Actual Effort – Estimated Effort)

——————————————  *  100

           Estimated Effort

 

 

Example

Consider a software project with a planned effort of 90 man-days and an actual effort of 115 man-days.

Planned Effort = 90
Actual Effort = 115

Effort variance =    (115 – 90)

————– * 100

90

= 27.77 %

 

As a project planning activity, effort slippage must be monitored continuously throughout the project. Effort slippage may lead to cost overruns. It is formally computed as a metric for phase ends in development projects. In the Spiral and Iterative development model, if the cycle time for each delivery is low (less than two months), it is calculated for each delivery.

Reasons

Effort variance can occur due to various reasons in a software project. Some of the reasons are as follows:

• Scope creep
• Resource Constraints
• Poor Planning
• Underestimation
• Unforeseen Issues

Scope Creep: Changes or additions to the project scope after the initial estimation can increase the effort required to complete the project, leading to slippage in effort and project timelines.

Resource Constraints: Inadequate resources, including human resources, tools, or infrastructure, can lead to inefficiencies and delays in completing tasks, contributing to effort slippage.

Poor Planning: Delays can result from ineffective project planning or execution practices, such as poor task prioritization, inefficient resource allocation, or lack of communication.

Underestimation: Initially underestimating the complexity or scope of the task or project. This often happens when insufficient information is available at the time of estimation or when assumptions turn out to be incorrect.

Unforeseen Issues: During the project execution phase, unexpected challenges, such as technical issues, dependencies on external factors, or changes in requirements, can arise.

 

Effort slippage is typically monitored and managed through regular project status updates, tracking actual effort against the planned effort, identifying root causes of slippage, and implementing corrective actions to mitigate its impact.