User Story and Feature Sizing and its Impacts
Reading Time: 10 Minutes
User stories are a fundamental building block. They are a simple, straightforward method of capturing product functionality from the perspective of the end-user. However, to effectively manage and deliver these user stories, teams need to understand their size and complexity. This is where user story sizing comes into play.
What is User Story Sizing?
User story sizing is a technique used in Agile software development to estimate the effort required to implement a user story. It involves assigning a relative size to each user story, which can then be used to plan sprints and manage workload.
Why is User Story Sizing Important?
User story sizing serves several purposes:
Planning and Forecasting: By understanding the size of a user story, teams can better plan and forecast their work. This helps in sprint planning and in predicting when work will be completed.
Prioritization: Size can influence the priority of a user story. Larger stories may be broken down into smaller ones to be tackled earlier if they are of high priority.
Communication: Sizing stories helps facilitate communication within the team. It provides a common language for discussing the complexity and effort required for each story.
How to Size User Stories?
There are several techniques for sizing user stories in Agile development:
1. T-Shirt Sizes
One of the simplest methods is to use t-shirt sizes (XS, S, M, L, XL). Each size represents a range of effort or complexity. For example, an XS might represent a story that can be completed in a day, while an XL might represent a story that could take a whole sprint.
Here’s how it functions:
Decide on Your Sizes: Prior to introducing t-shirt sizing to your team, determine the sizes you wish to use. Typical sizes include XS, S, M, L, XL, and XXL.
Align on What Each Size Represents: T-shirt sizing is effective only when everyone comprehends what each size signifies. Therefore, ensure your team understands what each size represents in terms of effort, complexity, or time.
Assign T-Shirt Sizes to Each Task: Based on its relative effort, assign a t-shirt size to each task or initiative. This assignment can be done collectively by the team or by specific individuals, depending on your team’s structure.
T-shirt sizing is frequently employed by engineering and software development teams, but it can be beneficial for any team. It’s a straightforward, intuitive method for estimating the size, complexity, or effort required for tasks or projects.
2. The Fibonacci Sequence
The Fibonacci sequence (1, 2, 3, 5, 8, 13, …) is another popular method for sizing user stories. The idea is that the size of a story is the sum of the sizes of its smaller parts. This method acknowledges that the uncertainty or complexity of work increases with size.
The Fibonacci sequence table shown here is simply a representative example and is used for demonstration purposes. As a result, the parameters may differ among various groups and industries.
3. Planning Poker
Planning poker is a consensus-based technique where team members make estimates by playing numbered cards face-down on the table, instead of speaking them aloud. Once everyone has played a card, they are revealed, and the estimates are then discussed.
Here’s a brief guide on how to use Planning Poker for Agile teams:
Understand the Basics: Planning Poker, also known as Scrum Poker, is a consensus-based technique for estimating the effort or relative size of tasks in software development. It’s commonly used in Agile teams.
Gather the Team: Include all members of the development team. Each member should have a set of Planning Poker cards with values like 0, 1, 2, 3, 5, 8, 13, 20, 40, and 100. These cards serve the purpose of estimating the effort needed to accomplish a task. The numbers are approximately in line with the Fibonacci sequence, providing a balance between exactness and ambiguity. As the number increases, it signifies a higher estimated effort for the task.
The infinity card (∞) signifies a task that is deemed too vast or intricate to quantify with a numerical value. Essentially, it translates to “This task is beyond numerical estimation.” When a team member opts for this card, it typically suggests that the task requires decomposition into smaller, more comprehensible segments for accurate estimation. It serves as a communication tool for the team to express the need for additional information or dialogue to grasp the task’s scope.
The question mark card (?) comes into play when a team member is uncertain about the estimate or lacks sufficient information to provide an accurate estimate. It serves as a medium for the team member to express their need for additional information or dialogue to comprehend the task's scope. Following more in-depth discussion or clarification, the team member is then able to provide a more informed estimate.
The coffee cup card is utilized when a team member feels the need for a break or wishes to pause the estimation process. This card is typically represented by an image of a steaming coffee cup. This card serves as a communication tool for the team to express their need for a brief respite before resuming the estimation process.
The 1/2 card is sometimes utilized to denote a task that is perceived to require a relatively minor amount of effort to accomplish and facilitates more detailed estimates for smaller tasks. The frequency of its usage is contingent upon the team and the nature of the tasks being estimated. Teams dealing with a multitude of small tasks might find themselves frequently resorting to the 1/2 card, while others might use it sparingly.
Explain the Task: The product owner or customer reads an agile user story or describes a feature to the estimators.
Discuss: Team members discuss the feature, asking questions of the product owner as needed. When the feature has been fully discussed, each estimator privately selects one card to represent his or her estimate.
Reveal Cards: All cards are then revealed at the same time.
Address Differences: If there is a large difference in estimates, the estimators discuss their estimates. The high and low estimators should especially share their reasons.
Repeat Estimation: After further discussion, each estimator reselects an estimate card, and all cards are again revealed at the same time. This process is repeated until consensus is achieved or until the estimators decide that agile estimating and planning of a particular item needs to be deferred until additional information can be acquired.
Record the Estimate: The estimate becomes part of the iteration plan. The team moves to the next user story.
The goal of Planning Poker is not to arrive at perfect estimates, but to provide a reliable framework for team discussion and collaboration. It’s about understanding what needs to be done and achieving consensus on the relative effort involved.
4. CONSIDER OTHER SIZING TECHNIQUES
Apart from T-Shirt Sizes, Fibonacci Sequence, and Planning Poker, there are several other techniques used for sizing user stories and features in Agile software development:
Dot Voting: In this technique, each team member is given a set number of "dots" or votes. They distribute their votes among the user stories to indicate the size or complexity. The more dots a story gets, the larger it is.
Affinity Estimating: This is a method where user stories are grouped by similarity. The team collectively decides which stories are small, medium, large, etc., based on their complexity or effort required.
Bucket System: This is similar to Affinity Estimating, but uses a set number of buckets. Each bucket represents a size (e.g., 1, 2, 3, 5, 8, etc.), and user stories are placed in the appropriate bucket.
Proportional Estimating: This technique involves comparing user stories to one another to determine their relative size. For example, if one story is considered twice as large as another, it would be given a size that is twice as large.
Ideal Days: This technique involves estimating the size of a user story based on how many "ideal" workdays it would take to complete. An "ideal" day is a day without meetings, interruptions, or other distractions.
Sizing in hours and T-shirt sizing are two different techniques used in Agile methodologies to estimate the effort required to complete a user story or feature.
Here’s how they work and how they relate to each other:
Sizing in Hours
Sizing in hours, also known as hourly estimation, involves estimating the number of hours it will take to complete a task. This is a more traditional method of estimation and is often used in waterfall methodologies, but it can also be applied in Agile.
Advantages
Precision: Sizing in hours can provide a more precise estimate, which can be helpful for planning and scheduling.
Familiarity: Most people are familiar with time-based estimates, making it easier to understand for stakeholders outside the development team.
Disadvantages
Overemphasis on Precision: Teams might spend too much time trying to get the “perfect” estimate, which can lead to analysis paralysis.
Lack of Flexibility: Hourly estimates do not account for the inherent uncertainty and variability in software development.
T-Shirt Sizing
T-shirt sizing involves assigning a size (XS, S, M, L, XL) to each user story or feature based on its relative complexity or effort compared to other stories.
Advantages
Simplicity: T-shirt sizes are easy to understand and use, making them a good fit for Agile teams.
Focus on Relative Size: T-shirt sizing emphasizes the relative size of stories, which is more important in Agile methodologies.
Disadvantages
Lack of Precision: T-shirt sizes are less precise than hour-based estimates, which can make scheduling and planning more challenging.
Subjectivity: The meaning of each size can vary among team members, leading to potential misunderstandings.
Relationship Between Sizing in Hours and T-Shirt Sizing
While both methods aim to estimate the effort required to complete a user story or feature, they approach it from different angles. Sizing in hours is a more precise, time-based estimate, while T-shirt sizing is a more abstract, relative estimate.
In practice, teams might use a combination of both methods. For example, a team might use T-shirt sizing during backlog refinement to quickly estimate the relative size of stories. Then, during sprint planning, they might break down the stories into tasks and use sizing in hours for a more detailed estimate.
The goal of both methods is not to create a perfect estimate, but to provide a useful tool for planning and managing work. The best method depends on the team’s needs, the nature of the work, and the team’s experience and skill level.
Now let’s dive deeper into the benefits and challenges of user story sizing.
Benefits of User Story Sizing
Improved Estimation: User story sizing allows teams to make better estimates about the time and effort required to complete a story. This leads to more accurate planning and forecasting.
Enhanced Prioritization: By understanding the size of a story, teams can prioritize their work more effectively. Larger stories might be broken down into smaller ones to be tackled earlier if they are of high priority.
Better Communication: Sizing provides a common language for the team. It facilitates discussions about the complexity and effort required for each story, leading to a shared understanding among team members.
Increased Efficiency: Over time, teams get better at sizing and understanding their velocity, which can lead to increased efficiency and productivity.
Challenges of User Story Sizing
Subjectivity: Sizing is subjective and can vary among team members. It’s important to reach a consensus, but this can be time-consuming.
Changing Requirements: As teams gain more knowledge about a story or its requirements change, the size of the story can change. This requires re-sizing and re-planning.
Overemphasis on Precision: Teams might spend too much time trying to get the “perfect” estimate. However, the goal of sizing is not to create a perfect estimate, but to understand the relative effort and complexity.
Difficulty in Comparing Sizes: It can be challenging to compare sizes across different teams or projects as the understanding of size can vary.
While user story sizing has its challenges, the benefits it brings to planning, communication, and efficiency make it an essential practice in Agile software development. It’s important to remember that the goal of sizing is to help teams plan and communicate, not to create a perfect estimate. With practice and experience, teams can overcome these challenges and effectively size their user stories.
Feature Sizing in Agile Software Development
While user stories are a fundamental unit of work in Agile, sometimes it’s necessary to think at a higher level of abstraction. This is where features come into play. A feature is a chunk of functionality that delivers considerable value but is larger than a single user story.
Just like user stories, features also need to be sized to help with planning and prioritization. Here’s how you can approach feature sizing:
1. Break Down the Feature
The first step in feature sizing is to break down the feature into smaller, manageable user stories. This can be done during a feature breakdown workshop involving the product owner, scrum master, and development team.
2. Size the User Stories
Once the feature has been broken down into user stories, size each user story using the techniques mentioned earlier (T-Shirt Sizes, Fibonacci Sequence, Planning Poker).
3. Aggregate the Sizes
Add up the sizes of all the user stories to get the total size of the feature. This gives an estimate of the total effort required to implement the feature.
4. Consider the Complexity
Remember to consider the complexity and uncertainty of the feature as a whole. Sometimes, the sum of the parts does not equal the whole. If the feature is complex or has many unknowns, consider adding a complexity buffer to the size.
Benefits of Feature Sizing
Better Planning: Feature sizing allows for better release and roadmap planning. It helps in understanding when a feature might be delivered.
Improved Prioritization: By understanding the size of a feature, product owners can make more informed decisions about feature prioritization.
Enhanced Stakeholder Communication: Feature sizing helps in setting stakeholder expectations about delivery timelines.
Challenges of Feature Sizing
Increased Complexity: Features are larger and more complex than user stories, making them harder to size accurately.
Changing Sizes: Just like user stories, the size of features can change as more is learned about the feature or if requirements change.
Overemphasis on Precision: Teams might spend too much time trying to get the “perfect” estimate for a feature. Remember, the goal is not to create a perfect estimate, but to understand the relative effort and complexity.
Feature Sizing
Similar to user story sizing, feature sizing is an essential practice in Agile software development. It helps teams plan, prioritize, and communicate at a feature level. Despite its challenges, with practice and experience, teams can effectively size their features and deliver value to their customers.
Impact of User Story and Feature Sizing on Software Release Management
Software release management is a critical aspect of the software development lifecycle. It involves planning, scheduling, and controlling a software build through different stages and environments, including testing and deploying software releases.
User story and feature sizing play a significant role in software release management. Here’s how:
1. Release Planning
In Agile development, release planning is a high-level process that outlines the project’s direction. It’s here that feature and user story sizing contribute significantly. By knowing the size (effort, complexity) of each user story and feature, teams can better plan which ones should be included in a release. This helps in setting realistic goals and expectations for a release.
2. Release Scheduling
Sizing helps in scheduling the releases. Teams that have a good understanding of their velocity (amount of work they can complete in a sprint) can use the sizes of the user stories and features to forecast when they will be ready for release.
3. Risk Management
Larger features and user stories often carry more risk (due to increased complexity and uncertainty). By identifying these large items through sizing, teams can manage these risks early, for example, by breaking down large features or stories into smaller, manageable ones.
4. Stakeholder Communication
Sizing helps in setting expectations with stakeholders. By communicating the size of the work, stakeholders get a better understanding of what can be delivered in a release.
5. Continuous Improvement
Over time, as teams get better at sizing and estimating their work, they can improve their release management processes. They can become more accurate in their plans and forecasts, leading to more successful releases.
User story and feature sizing are essential practices in Agile software development that significantly impact software release management. They aid in planning, scheduling, risk management, stakeholder communication, and continuous improvement, contributing to more successful and predictable software releases.
Sizing Example
User Story & Feature Sizing Example
This table represents the relative effort required to implement each user story or feature. These sizes are relative to each other and don’t represent a specific amount of time or effort. The actual effort might vary based on the team’s capability, technical complexity, and other factors. The goal is to help with planning and prioritization.
In this example:
“Login functionality” is a small (S) task, meaning it’s relatively simple to implement.
“User profile creation” is a medium (M) task, which might involve more work than the login functionality.
“Implementing search functionality” is a large (L) task, indicating it’s more complex or time-consuming.
“Adding shopping cart functionality” is an extra-large (XL) task, which might involve multiple sub-tasks and considerable effort.
“Integrating payment gateway” is an extra-extra-large (XXL) task, suggesting it’s the most complex and might need to be broken down into smaller tasks.
When to use Feature and User Story Sizing Techniques
In Scrum, the sizing of features and user stories typically happens during two key ceremonies: Backlog Refinement (Grooming) and Sprint Planning.
Backlog Refinement (Grooming): This is a recurring meeting where the Product Owner and the Development Team review items on the product backlog to ensure the backlog contains the appropriate items, that they are prioritized, and that the items are prepared for upcoming sprints. During this meeting, new user stories and features can be introduced, existing ones can be clarified or redefined, and most importantly, initial sizing or re-sizing can be done. This is where T-shirt sizing or Fibonacci sequence (or any other preferred method) is used to estimate the relative effort of work.
Sprint Planning: This is the ceremony that kicks off the sprint. The Product Owner, Scrum Master, and the Development Team collaborate to decide what user stories and features will be worked on during the upcoming sprint. The team sizes or re-sizes the selected user stories or features based on any new information or understanding gained since the Backlog Refinement meeting. The goal is to ensure that the team commits to an achievable amount of work for the sprint.
Scientific Principles and Quantifiable Measures
User story and feature sizing are essential practices that help teams plan, prioritize, and manage their work. These practices are based on the principle of relative estimation, where the size or effort of a user story or feature is compared to others, rather than being measured in absolute terms such as hours or days.
Here’s an explanation of these practices and their relation to quantifiable measures:
Relative Estimation: This is the principle behind user story and feature sizing. It’s based on the observation that humans are better at comparing things than at absolute estimation. By comparing the size or effort of a user story or feature to others, teams can create a more accurate and reliable estimate.
Velocity: This is a key metric in Agile development that measures the amount of work a team can complete in a sprint. It’s calculated by adding up the sizes of all user stories or features completed in a sprint. By knowing their velocity, teams can better plan and forecast future sprints.
Effort-Duration Relationship: In project management, there’s a well-known relationship between effort and duration: as effort increases, the duration also increases, but at a decreasing rate. This is due to factors such as task concurrency and fatigue. User story and feature sizing take this relationship into account, which is why many teams use a non-linear scale (like the Fibonacci sequence) for sizing.
Cone of Uncertainty: This is a model used in software development to represent the uncertainty that decreases over time as more knowledge is gained. At the start of a project, estimates can be very inaccurate, but as the team progresses, the estimates become more reliable. User story and feature sizing are iterative processes that should be revisited as more is learned about the requirements and the team’s capabilities.
Law of Large Numbers: This law states that as the number of trials increases, the average result gets closer to the expected value. In the context of Agile development, this means that while individual user story or feature estimates may be off, the total estimate for a large number of user stories or features is likely to be accurate.
User story and feature sizing are not just arbitrary practices, but are grounded in scientific principles and quantifiable measures. They provide a practical and effective way for Agile teams to plan their work and set themselves up for success in software development.
Personal Thoughts: Does Sizing Work?
I find feature and user story sizing to be incredibly helpful in my work. It’s like having a compass that guides us through our Agile journey. By understanding the size and complexity of each user story or feature, we can better plan our sprints and manage our workload. It helps us set realistic goals and expectations, which is crucial for maintaining a sustainable pace of work.
What I appreciate most about sizing is that it’s not just about numbers or estimates. It’s a conversation starter. It sparks discussions about the work we’re doing, the challenges we might face, and how we can overcome them. It brings the team together and helps us build a shared understanding of our work.
Sure, it’s not always easy. There are times when we struggle to agree on a size, or when a user story turns out to be larger than we expected. But that’s okay. It’s all part of the learning process. With each sprint, we get better at it. And that’s what Agile is all about - continuous improvement.
So yes, I feel pretty positive about feature and user story sizing. It’s not just a tool, but a key part of our Agile mindset.
But there have been incidences when underestimating and overestimating the size of features and user stories can have significant impacts on the sprint and the overall project. Here’s what happened in my experience and what might happen to you and your team(s):
Underestimation:
Increased Pressure: If a user story or feature is larger than estimated, it can lead to increased pressure on the team to meet the sprint commitment, which can result in overtime work and burnout.
Quality Issues: In an attempt to complete the work within the sprint, the team might take shortcuts, leading to quality issues and technical debt.
Incomplete Work: The user story or feature might not be completed within the sprint, leading to carryover work for the next sprint.
Overestimation:
Reduced Productivity: If a user story or feature is smaller than estimated, the team might end up with idle time, reducing the overall productivity.
Missed Opportunities: Overestimation can lead to missed opportunities as the team could have committed to and completed more work.
Inaccurate Velocity: Overestimation can inflate the team’s velocity, leading to inaccurate forecasting for future sprints.
To address these issues, teams can take the following steps:
Retrospective Analysis: At the end of each sprint, conduct a retrospective to discuss what went well and what didn’t. If there were significant estimation errors, try to understand why they occurred and how they can be avoided in the future.
Refinement: Regularly refine the product backlog. As the team gains more knowledge about the product and the technology, update the sizes of the user stories and features.
Training: Provide training and coaching to the team on estimation techniques. Remember, estimation is a skill that improves with practice.
Break Down User Stories and Features: If a user story or feature is too large and difficult to estimate, break it down into smaller, more manageable pieces.
Use Historical Data: Use historical data about the team’s performance and past sprints to inform future estimates.
Remember, the goal of estimation is not to get a perfect estimate, but to provide a useful tool for planning and managing work. It’s okay if estimates are not always accurate; what’s important is that the team learns from the experience and continuously improves its estimation process.
My Research References
Here are some references to case studies and articles that I personally researched that discuss their use and effectiveness:
The article “Agile Estimation – Feature and Story Sizing Scales” discusses the importance of developing a simple, repeatable scale for feature-level sizing and story point estimating. It emphasizes that the estimating scale touches every part of the release as well as each sprint, making it crucial for successful release delivery.
The article “Size Estimation Approaches for Use with Agile Methods” provides an overview of different size estimation approaches used in Agile methods. It discusses the need for software size estimates at the project level and higher for various purposes, including scoping the time and effort needed to deliver quality software products, assessing risks, and making strategic decisions.
These references provide evidence that feature and user story sizing can work effectively in Agile software development. However, it’s important to note that their effectiveness can depend on various factors, including the nature of the project, the experience and skill level of the team, and the specific practices and methodologies used by the team.
