Understanding Velocity in Scrum and Its Predictive Power

Velocity is a common metric used by Scrum Teams to measure the amount of work completed during a Sprint. It is often used as a historical record to help predict how much work can be done in future Sprints. However, while velocity can provide useful insights, its reliability as a predictive tool is not absolute and can be influenced by various factors.

Exam Question

Scrum Teams often use velocity as a technique to measure historical output. How useful is historical velocity to a Scrum Team for predicting future velocity, even of the next Sprint? Provide two examples of what might cause velocity to be unreliable.

Explanation

The Usefulness of Historical Velocity

• Estimating Future Workload: Historical velocity can give the Scrum Team a general idea of how much work they can complete in a Sprint based on past performance. It can help in planning and forecasting, providing a baseline for what the team might achieve in the upcoming Sprint.
• Facilitating Sprint Planning: Teams often use their average velocity to decide how many Product Backlog items to select for the next Sprint. This approach can help prevent over-committing and under-delivering, as it is based on the team’s demonstrated capacity.

However, historical velocity is not always a reliable predictor of future performance.

Factors That May Cause Velocity to Be Unreliable

• Changes in Team Composition: If the team’s composition changes—such as adding new team members, losing experienced ones, or even temporary unavailability of key members—velocity can be significantly affected. A new team member might need time to get up to speed, or the absence of a key team member could reduce the team’s capacity.
• Variability in Work Complexity: Not all Sprints are created equal. The complexity of the work taken on during a Sprint can vary widely. If a Sprint includes more complex or unfamiliar tasks, it may slow down the team’s progress, leading to a lower velocity than expected. Conversely, a Sprint filled with less complex tasks might artificially inflate velocity.
• Unplanned Work and Interruptions: Unplanned work, such as urgent bug fixes or sudden high-priority requests, can disrupt the team’s planned work and reduce velocity. Additionally, interruptions like meetings, company events, or technical issues can decrease the team’s focus and productivity, leading to a lower-than-expected velocity.

Relevance to the PSM III Exam

In the PSM III exam, understanding the limitations and contextual factors affecting Scrum metrics like velocity is crucial. Scrum Masters must be able to facilitate discussions on these topics, ensuring that the team and stakeholders understand the implications of relying too heavily on historical velocity for planning future Sprints.

Key Takeaways

• Historical velocity provides a baseline but is not an infallible predictor of future performance.
• Team composition and work complexity are key factors that can cause velocity to fluctuate.
• Scrum Teams should use velocity as one of several tools for planning, but remain flexible and ready to adapt to changes.

Conclusion

While velocity is a useful metric for understanding a Scrum Team’s capacity over time, it should not be the sole factor in predicting future performance. Teams must consider the context of each Sprint, including changes in team composition and the complexity of work, to make more accurate predictions. For more insights into Scrum practices and preparing for the PSM III exam, visit our Scrum Master PSM III™ Exam Prep.