PMI-ACP Practice Questions #87
During backlog refinement, your Agile team is estimating user stories for a health tracking mobile app. A new team member notices that the team assigns story points using the Fibonacci sequence (1, 2, 3, 5, 8, 13, etc.) instead of consecutive numbers (1, 2, 3, 4, 5, etc.) and asks why this approach is used.
As an Agile Coach, how should you explain the reason for using the Fibonacci sequence in story point estimation?
A. The Fibonacci sequence introduces randomness into estimates, making them less predictable and harder to challenge.
B. Using Fibonacci numbers helps the team differentiate between small, medium, and large stories more clearly, improving estimation accuracy.
C. Fibonacci numbers force the team to estimate larger stories higher, preventing developers from underestimating tasks.
D. It reflects the increasing uncertainty as story sizes grow, helping teams avoid false precision in large estimates.
Analysis
During backlog refinement, the Agile team estimates user stories using the Fibonacci sequence. A new team member questions why Fibonacci numbers are used instead of consecutive numbers. The core idea behind using Fibonacci numbers in Agile estimation is that as the story size increases, the level of uncertainty also grows. Larger stories have more unknowns, making precise estimation difficult. The Fibonacci sequence helps teams account for this increasing uncertainty by providing a non-linear progression, which prevents the illusion of precision when estimating larger tasks.
Analysis of Options
A: The Fibonacci sequence introduces randomness into estimates, making them less predictable and harder to challenge.
This is incorrect. The Fibonacci sequence is not used to introduce randomness; rather, it introduces structured gaps between estimates to reflect increasing uncertainty. The goal is to improve estimation accuracy, not to make estimates unpredictable or difficult to challenge.
B: Using Fibonacci numbers helps the team differentiate between small, medium, and large stories more clearly, improving estimation accuracy.
This is partially correct. The Fibonacci sequence does help differentiate between different sizes of user stories, but the primary reason for using it is not just classification—it is to reflect the growing uncertainty of larger stories. While this option is somewhat valid, it does not fully capture the core reason behind using Fibonacci numbers.
C: Fibonacci numbers force the team to estimate larger stories higher, preventing developers from underestimating tasks.
This is incorrect. The Fibonacci sequence does encourage higher estimates for larger stories, but its purpose is not to “force” teams to estimate larger. The goal is to reflect natural uncertainty rather than artificially inflating estimates. Additionally, Agile estimation is a team activity, not just for developers.
D: It reflects the increasing uncertainty as story sizes grow, helping teams avoid false precision in large estimates.
This is the correct answer. The Fibonacci sequence is used because as the complexity and size of a story increase, the ability to estimate it accurately diminishes. The gaps between Fibonacci numbers help teams avoid the illusion of precision in larger estimates and encourage breaking down large stories into smaller, manageable ones.
Conclusion
The best answer is Option D, as it accurately explains the primary reason for using Fibonacci numbers in Agile estimation—to account for increasing uncertainty and avoid false precision when estimating larger stories. Options A, B, and C either provide incomplete or incorrect explanations.
PMI – ACP Exam Content Outline Mapping
| Domain | Task |
| Product | Refine Product Backlog |
Topics Covered:
- Fibonacci sequence accounts for increasing uncertainty in large stories
- Helps avoid false precision in estimation
- Encourages breaking down large stories into smaller, manageable ones
- Differentiates between small, medium, and large user stories
If you’re preparing for the PMI Agile Certified Practitioner (PMI-ACP)® Exam, we highly recommend enrolling in our PMI-ACP® Exam Prep Program. Designed to provide a comprehensive Agile learning experience, this program not only helps you ace the PMI-ACP® exam but also enhances your Agile mindset, leadership skills, and ability to deliver value-driven projects. Ensure exam success and career growth with our expert-led, structured preparation program tailored for Agile professionals.
