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Tuesday, July 08, 2014

What is an Estimate?

If you don’t know what an estimate is, you can’t avoid using them. So here’s my attempt to define what is an estimate.
The "estimates" that I'm concerned about are those that can easily (by omission, incompetence or malice) be turned into commitments. I believe Software Development is better seen as a discovery process (even simple software projects). In this context, commitments remove options and force the teams/companies to follow a plan instead of responding to change.

Here's my definition: "Estimates, in the context of #NoEstimates, are all estimates that can be (on purpose, or by accident) turned into a commitment regarding project work that is not being worked on at the moment when the estimate is made."

The principles behind this definition of an estimate

In this definition I have the following principles in mind:
  • Delay commitment, create options: When we commit to a particular solution up front we forego possible other solutions and, as a consequence we will make the plan harder to change. Each solution comes with explicit and implicit assumptions about what we will tackle in the future, therefore I prefer to commit only to what is needed in order to validate or deliver value to the customer now. This way, I keep my options open regarding the future.
  • Responding to change over following a plan: Following a plan is easy and comforting, especially when plans are detailed and very clear: good plans. That’s why we create plans in the first place! But being easy does not make it right. Sooner or later we are surprised by events we could not predict and are no longer compatible with the plan we created upfront. Estimation up front makes it harder for us to change the plan because as we define the plan in detail, we commit ourselves to following it, mentally and emotionally.
  • Collaboration over contract negotiation: Perhaps one of the most important Agile principles. Even when you spend time and invest time in creating a “perfect” contract there will be situations you cannot foresee. What do you do then? Hopefully by then you’ve established a relationship of trust with the other party. In that case, a simple conversation to review options and chose the best path will be enough. Estimation locks us down and tends to put people on the defensive when things don’t happen as planned. Leaving the estimation open and relying on incremental development with constant focus on validating the value delivered will help both parties come to an agreement when things don’t go as planned. Thereby focusing on collaboration instead of justifying why an estimated release date was missed.
  Here are some examples that fit the definition of Estimates that I outlined above:
  • An estimate of time/duration for work that is several days, weeks or months in the future.
  • An estimate of value that is not part of an experiment (the longer the time-frame the more of a problem it is).
  • A long term estimate of time and/or value that we can only validate after that long term is over.

How do you define Estimates in your work? Are you still doing estimates that fit the definition above? What is making it hard to stop doing such estimates? Share below in the comments what you think of this definition and how you would improve it.

This definition of an estimate was sent to the #NoEstimates mailing list a few weeks ago. If you want to receive exclusive content about #NoEstimates just sign up below. You will receive a regular email on the topic of #NoEstimates as Agile Software Development.

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Tuesday, July 01, 2014

What is Capacity in software development? - The #NoEstimates journey


I hear this a lot in the #NoEstimates discussion: you must estimate to know what you can deliver for a certain price, time or effort.

Actually, you don’t. There’s a different way to look at your organization and your project. Organizations and projects have an inherent capacity, that capacity is a result of many different variables - not all can be predicted. Although you can add more people to a team, you don’t actually know what the impact of that addition will be until you have some data. Estimating the impact is not going to help you, if we are to believe the track record of the software industry.

So, for me the recipe to avoid estimates is very simple: Just do it, measure it and react. Inspect and adapt - not a very new idea, but still not applied enough.

Let’s make it practical. How many of these stories or features is my team or project going to deliver in the next month? Before you can answer that question, you must find out how many stories or features your team or project has delivered in the past.

Look at this example.

How many stories is this team going to deliver in the next 10 sprints? The answer to this question is the concept of capacity (aka Process Capability). Every team, project or organization has an inherent capacity. Your job is to learn what that capacity is and limit the work to capacity! (Credit to Mary Poppendieck (PDF, slide 15) for this quote).

Why is limiting work to capacity important? That’s a topic for another post, but suffice it to say that adding more work than the available capacity, causes many stressful moments and sleepless nights; while having less work than capacity might get you and a few more people fired.

My advice is this: learn what the capacity of your project or team is. Only then you will be able to deliver reliably, and with quality the software you are expected to deliver.

How to determine capacity?

Determining the capacity of capability of a team, organization or project is relatively simple. Here's how

  • 1- Collect the data you have already:
    • If using timeboxes, collect the stories or features delivered(*) in each timebox
    • If using Kanban/flow, collect the stories or features delivered(*) in each week or period of 2 weeks depending on the length of the release/project
  • 2- Plot a graph with the number of stories delivered for the past N iterations, to determine if your System of Development (slideshare) is stable
  • 3- Determine the process capability by calculating the upper (average + 1*sigma) and the lower limits(average - 1*sigma) of variability

At this point you know what your team, organization or process is likely to deliver in the future. However, the capacity can change over time. This means you should regularly review the data you have and determine (see slideshare above) if you should update the capacity limits as in step 3 above.

(*): by "delivered" I mean something similar to what Scrum calls "Done". Something that is ready to go into production, even if the actual production release is done later. In my language delivered means: it has been tested and accepted in a production-like environment.

Note for the statisticians in the audience: Yes, I know that I am assuming a normal distribution of delivered items per unit of time. And yes, I know that the Weibull distribution is a more likely candidate. That's ok, this is an approximation that has value, i.e. gives us enough information to make decisions.

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