The entire series on estimation has focused on the inherent problems of time-based estimates. We introduced and recommended story points as a more viable option to time estimates. In this series finale article, we look at story point estimation more closely and understand how it resolves the issues that crop up with time estimates.
Creates confidence by asking the right questions
A prime concern with time estimates is that they are almost always wrong. That’s because you’re asking too complex a question–combining two aspects, viz., how big something is and how fast you can go. Story point estimation makes things easier at the very outset by separating these two questions.
Further, it simplifies the “How big?” question by asking how big the stories are relative to a benchmark we’ve set, which is typically the smallest story in the backlog. This process of Relative Sizing or allocating a size to a story by comparing it with a standard can be completed quickly. In addition to speed, this process generates a high level of confidence in the sizes. Infact, we need not call them estimates at all; they are definite sizes. There is no scope for ambiguity and there is no need to revisit or change the sizes.
The second of the 2 sub-questions that story points ask is “How fast can you go?”. We admit upfront that nobody really knows the answer. So we move on to the next best way to approach this question and that’s through informed and logical guesswork–using the exercise of Raw Velocity. This involves multiple developers picking up multiple and diverse items from the backlog with their estimates hidden and stating which ones they can finish in a given time period (an iteration). Then we add up the estimates for the items that were picked up to find the “gut feel” of the story points that can be completed in an iteration. We do this math over several rounds with each of the developers. The average derived thus reflects a gut feeling of the majority of the team regarding the time required to complete the given backlog.
While it’s accepted as guesswork, these numbers evoke a higher level of confidence because the developers have answered a comparatively easier question–regarding their own capabilities and not that of someone else. Hence the answer is likely to be accurate.
Moreover, we use the Raw Velocity numbers only for a short duration – during the first couple of iterations. After those initial iterations, we are in a position to make more informed velocity calculations because we have real data from the real work done during the first few iterations. Going forward, we use our judgement based on this data and not on the guesswork we started out with. Thus the answer to “How fast?” is now rooted in accuracy and we can proceed with confidence and conviction in our sign-up for the subsequent iteration.
Story point estimation, thus, instills confidence by asking the right questions. The responses to these questions leave no room for confusion or doubt. From one question we get definite sizes and the response to the other is grounded in real data. We can successfully avoid the feeling of being wrong–which is typically what happens in time estimation. On the contrary, we are now confident and convinced about how much the team can do especially in the short term.
Time-based estimation also creates pressure–at the 2 stages of estimation and execution. Let’s dive deep…
There are 2 problem-creating scenarios with time estimates during the estimation
- The compound question that kickstarts time estimation is itself a pressure point because you’ve mixed up 2 sub-questions. In an attempt to respond to that compound question, you try to cover all possible scenarios and come up with precise numbers. Too much time is spent on seeking too many details too early on.
- The other problem is that you have too many options to choose from in terms of time period. This wide range of choices significantly raises the probability of errors. You may end up either over- or under-estimating. In either case, you end up feeling pressured. Typically you will react to such pressure by being extra vigilant about every possible scenario or then by adding buffers to play it safe.
Story point estimation has no scope for such problems. Firstly, it limits the number of size options to just 3 or 4. All we’re doing is picking up each story and comparing it to a sample set in terms of size. Once we’ve assigned a size, it’s frozen. We don’t need any more details; we don’t need to revisit the sizes. The issues–and consequent pressure–of time estimates do not even exist in the story points world.
In a time estimates scenario, you may realize that the size of the task is different from what was assumed during planning, or that the pace of work is getting affected by extraneous conditions. However, you’ve already committed to getting an X amount of work done in a given time-frame. You naturally feel pressured because time is running out.
Story points avoid this pressure by setting the right expectations from the start. We are cognizant that Raw Velocity is a guess and those numbers will change in the face of real work. We take a cue from previously completed iterations and incorporate those learnings into Estimated Velocity. The guesswork progresses into informed estimation, which definitely has more value. Over time, this boosts the team’s confidence too.
Replaces negative pressure with positive ambition
Using Relative Sizing and Velocity, we’ve eliminated the pressure of completing an X amount of work in a given period of time. With that pressure gone, what we experience is a positive emotion and the aspiration and ambition to strive for continuous delivery and improvement.
Having sifted out questions that have no real meaning, we zone in on the most relevant ones in our effort to achieve continuous delivery – What should we take up in the next iteration? What will be of highest value to go next? With these questions, we strive to make the delivery process better, more productive and centered around excellence.
Empowers the team
Story points create a transition from individual performance and individual goals to team goals. The commitment now is to put out a set of features into production. The onus is on the team as a whole and so developers are likely to help each other and even help other roles to complete what has been started. There is no rush to start new items from the backlog. The emphasis is on completing what’s been started–in the right sequence, with the right quality, with mutual collaboration as a team. The debilitating competitive pressure gives way to a positive environment and a collective intention to achieve. The atmosphere is still charged with high intensity, but it’s energizing and collaborative.
Retains the focus on completion
At this point, it’s important to remember that story points work around a rule of averages without any direct conversion of points into days. If we still did the conversion in our minds , we would lose some of the benefits intrinsic to this type of estimation. There can be no blanket rule that a story of X points will always get done in Y days. Conditions are fluid and each story and each developer has their own pace. If this is accepted, then we’ve reduced some of the pressure of dates and time commitments faced by developers.
However, it’s imperative to be aware that doing away with the pressure of time commitments does not equate to development meandering along at its own pace or the absence of accountability around completion. We definitely must ask these pertinent questions, but with the intention and aim of removing impediments and achieving progress. The ticking clock must not be allowed to assume nightmarish proportions. Developers should breathe easy and strive for excellence and continuous improvement instead of struggling for self-preservation.
Enables effective tracking
Time-based estimation poses a tracking hazard because we cannot segregate how much time was spent doing real development work and how much was lost in breaks or leaves. If we do attempt to track break and leave time, it would lead to micromanagement of the team, and we do not want to go there.
Separately, in time estimates, there is no way to apply the learnings from previous work to what will be taken up next. For example, if one story gets delayed, we cannot predict the time completion for the next story.
Story point estimation is able to counter such problems. Velocity is an average across multiple developers and multiple iterations. After the initial stories, the guesswork is replaced by insights gathered from real work and real data. We are in a good position to estimate how much time will be required to complete the next story, based on our learnings from previous iterations. This is valuable and it helps boost the team’s confidence in its own capabilities.
Similarly, if we have visibility into who’s going to be away next week, we count them out of capacity and make adjustments accordingly. For e.g., if the full team’s velocity is 10, we might only plan for 8, knowing that there will be 2 less on the team.
Clarity that results from learning from previous iterations or from accounting for leaves and breaks prevents us from erroneously concluding that the team hasn’t been working hard enough if our targets aren’t met. The team’s morale isn’t affected adversely and we stay focused on guiding the next iteration in the correct way, using practices that can ensure accomplishment and achievement as a team.
Targets continuous delivery even if project is lagging
Despite the best intentions and care, the project can go off track. Imagine that it’s not possible to meet the target of 10 points per iteration. At such a time, story point estimation adopts a rational problem-solving approach instead of mindlessly indulging in the blame game. Since XP’s version of the Golden Triangle keeps Scope variable, we can proceed by going live with the most important, prioritized stories on the said date. The rest of the features can get added over the next few iterations.
This ensures that we deliver on the committed date, even if it’s not the entire bulk of scheduled deliverables. This practice of Continuous Delivery instills confidence in the client stakeholders that there is no major delay harming the project. We’ve ensured that the most relevant features are already in production by the half-way mark, and what didn’t get completed will be delivered in the next few iterations, which will be just a couple of weeks out. We’ve succeeded in derisking the project to a large extent quite early in the game.
Story point estimation makes life better
At the end of this series, we’ve firmly established that story point estimation and the XP way of planning makes estimation easier and more accurate. It creates the right atmosphere for individuals and the team as a whole. Software quality and excellence remain the star of the show throughout. Harmful after-effects and negative behavior patterns arising out of pressure find no place in this process. Stakeholders also experience a high level of confidence as they get a clear view into the project’s progress and can take efficient and timely decisions in response to possible changes. Story point estimation is a win-win for all parties, and it’s the only effective method for project estimation and planning.