What is a Velocity Offset?
Difference between the promised and realised story points
Velocity expresses the average speed of a development team in Scrum. It is calculated from the sum of the story points realised per sprint divided by the number of sprints. The velocity offset is the sum of the planned but not realised story points per sprint. It is a measure of the deviation between planning and execution. With the help of the velocity chart, the velocity offset can be easily displayed.
Unimplemented user stories are usually rescheduled for subsequent sprints – alternatively, they could be postponed or abandoned altogether in the course of sprint planning. However, the greater the deviation between the number of story points promised and thus planned and the number of story points realised, the more important it becomes for the parties involved – the Product Owner, the Scrum Master and the development team – to discuss the issue. It is important to identify the cause of the velocity offset. Possibly
- the development team was too optimistic.
- the development team overlooked a technical context.
- absences, holidays or illnesses were overlooked.
- there were impediments that prevented the team from working.
- the Product Owner has planned more user stories against better knowledge and the Scrum Master has allowed this.
- there were unpredictable events such as short-term bug fixes that had a higher priority.
The calculation of velocity and velocity offset is often performed by the development team or, if required, by the Scrum Master.
Sometimes you can also read about a velocity offset factor that should be taken into account during sprint planning. This does not add any value to the planning because the velocity itself is already the measure of the average speed of the development team and thus the basis for the next sprint.
An assessment of the use of velocity in agile projects can be found here »