Skip to main content

Agile and Estimation

Over on Tyner Blain, Scott states:
"There is nothing that prevents a waterfall project from reviewing estimates throughout the course of the project."
Recall that agile processes use iteration and frequent releases to adjust to changing requirements and other discoveries during product development. Waterfall processes, on the other hand, schedule along a critical path that culminates in a single release.

While Scott endorses agile practices, he does not believe they lead to improved estimation. I don't agree with Scott on this last point. Here's why.

Reliable estimates hinge upon a holistic understanding of requirements, design, implementation, and testing.

With waterfall, you certainly can review and adjust estimates halfway through the process, but you will not be able to incorporate the full feedback effects. For example, you could be halfway through requirements and design and re-estimate the project, but you wouldn't have the benefit of the discoveries that inevitably occur during implementation and testing.

With incremental delivery (agile), you iterate on all of these phases early and often. Consequently, you quickly learn the impact of, for instance, testing on requirements. You are thus better informed when you review and adjust your estimates for the project.

Comments

Roger L. Cauvin said…
Scott, I think you're neglecting two important factors.

First, the learning that comes from incremental releases does not merely stem from feedback from stakeholders. We make requirements discoveries during design, implementation, and testing. We make design discoveries during implementation and testing. And so forth.

Second, you can generally make better informed estimate adjustments in an iterative process. You simply have more information to make the estimate due to having partially confronted the requirements, design, implementation, and testing risks on an iterative basis.

Better estimates are not merely a function of experience. They depend on information. Iterative processes bring to light the information with the most impact early in the cycle.
Wed Apr 19, 11:48:00 AM 2006
Roger L. Cauvin said…
Just to be clear. You wrote:

"The feedback that comes from those end users doesn't change how long we estimate that it would take to implement X, it changes X to Y."

That's true, but the information we get from iterating isn't just what we will implement, but how long it will take to implement it.

For example, without changing the requirements in any way, we may find by iterating that the architecture is much more complex than originally anticipated, and that therefore the level of effort required to implement the same requirements will be higher than our original estimate.
Wed Apr 19, 12:01:00 PM 2006
Roger L. Cauvin said…
Scott, I see distinctions you're trying to make, but the terminology is not quite right. You write:

"I completely agree that design, implementation and testing are the sources of information that make our estimations better. My point is that we can do all of that with a waterfall process too."

and

"I chose to run that project in a continuous release-ready state. Every night we had an automated build and test cycle. We continuously applied the insights from our build and test findings to refine our estimates."

What you describe is not a pure waterfall process. A continuous or iterative release-ready state is characteristic of an agile approach, not a waterfall one.

You also write:

"These are the benefits that you are associating with incremental delivery. I associate these benefits with incremental construction. Since we didn't deliver to the customer and get feedback that allowed us to improve our requirements, it wasn't an incremental delivery process."

You make an important distinction between incremental delivery and incremental construction. Even so, the notion of "delivery" is actually itself ambiguous. Some advocates of incremental delivery don't believe it's essential in every "release" to deliver product to a customer. You can realize a lot of benefits beyond mere incremental development if you deliver the product to your own team as if you were delivering to a customer.

Either way, incremental delivery entails incremental development, which does improve estimation in a manner that pure waterfall processes cannot.
Wed Apr 19, 11:46:00 PM 2006
Post a Comment

Popular posts from this blog

Why Spreadsheets Suck for Prioritizing

The Goal As a company executive, you want confidence that your product team (which includes all the people, from all departments, responsible for product success) has a sound basis for deciding which items are on the product roadmap. You also want confidence the team is prioritizing the items in a smart way. What Should We Prioritize? The items the team prioritizes could be features, user stories, epics, market problems, themes, or experiments. Melissa Perri  makes an excellent case for a " problem roadmap ", and, in general, I recommend focusing on the latter types of items. However, the topic of what types of items you should prioritize - and in what situations - is interesting and important but beyond the scope of this blog entry. A Sad but Familiar Story If there is significant controversy about priorities, then almost inevitably, a product manager or other member of the team decides to put together The Spreadsheet. I've done it. Some of the mos...
32 comments
Read more

5 Ways Companies Make Product Decisions

In the last blog entry, we reviewed the  four problems that companies face, or are trying to overcome, as they make product decisions .  Now we'll look at the ways that most companies make their product decisions. Companies that develop, market, and sell products and solutions make strategic and ongoing tactical decisions.  They decide what features to include in their products, what messages they will use to communicate the value of their products, what marketing tactics they will use, what prospective customers they will target, and many day-to-day choices. Whether or not these decisions are deliberate or ad hoc, most companies use some combination of the following ways of making product decisions. (A downloadable "map" that summarizes the product decision landscape is included at the end of this article.) Customer Wants Product decisions based on feature requests, focus groups, and what prospects and customers say they want. Companies are selling products to ...
12 comments
Read more

Is Customer Development Pseudoscience?

The “Science” of Lean Startup Lean startup practitioners embrace the scientific method, seeking the "truth" about what business model and strategy will lead to product success. We do so by: Formulating hypotheses Crafting and running experiments to test them Learning from the experiments Iteratively feeding our learnings back into revised hypotheses Sounds pretty scientific, at least in spirit, doesn't it? Yet this process actually neglects a key ingredient in the scientists' mode of operation. To identify what’s missing, let’s examine “customer development”. Customer Development Steve Blank is one of the pioneers of the lean startup movement. He introduced into the lean startup lexicon the term “customer development”. Customer development consists of sessions and interactions with customers to test hypotheses. For example, a product manager might interview a prospect, asking if she agrees with the product manager’s hypotheses about the problems she faces or the ...
9 comments
Read more