Tag Archives: complexity

9 Agile Estimation Techniques

Many people have used a variation of Planning Poker to do Agile estimation.  Here is a reference of 9 different Agile estimation techniques for different circumstances.  I have seen all of these techniques work in practice, except one.  Try a new one each Sprint!

Planning Poker

Participants use specially-numbered playing cards to vote for an estimate of an item.  Voting repeats with discussion until all votes are unanimous.  There are lots of minor variations on Planning Poker.  Good technique to estimate a very small number of items (2 to 10).

The Bucket System

Using the same sequence as Planning Poker, a group or a team estimate items by placing them in “buckets”.  The Bucket System is a much faster Agile estimation technique than Planning Poker because there is a “divide-and-conquer” phase.  The Bucket System can also be used with larger groups than Planning Poker and with very large numbers of items to be estimated (50 to 500).

Big/Uncertain/Small

For super-fast Agile estimation, the items to be estimated are simply placed by the group in one of three categories: big, uncertain and small.  The group starts by discussing a few together, and then, like the Bucket System, uses divide-and-conquer to go through the rest of the items.

TFB / NFC / 1 (Sprint)

This Agile estimation technique is similar to Big/Uncertain/Small but puts a specific “size” into the mix, namely 1 Sprint.  The categories are “Too F-ing Big”, “No F-ing Clue” and “1” Sprint (or less).  I learned this one recently from someone in one of my CSPO classes.

Dot Voting

Dot voting is usually considered a decision-making tool, not an Agile estimation technique.  However, for estimating small numbers of items, dot voting can be a super-simple and effective technique.  Each person gets a small number of “dots” and uses them as votes to indicate the size of an item; more dots means bigger.

T-Shirt Sizes

Items are categorized into t-shirt sizes: XS, S, M, L, XL.  The sizes can, if needed, be given numerical values after the estimation is done.  This is a very informal technique, and can be used quickly with a large number of items.  Usually, the decisions about the size are based on open, collaborative discussion, possibly with the occasional vote to break a stalemate.  There is a brief description of T-Shirt Sizes here.

Affinity Mapping

Items are grouped by similarity – where similarity is some dimension that needs to be estimated.  This is usually a very physical activity and requires a relatively small number of items (20 to 50 is a pretty good range).  The groupings are then associated with numerical estimates if desired.

Ordering Protocol

Items are placed in a random order on a scale labeled simply “low” to “high”.  Each person participating takes turns making a “move”.  A move involves one of the following actions: change the position of an item by one spot lower or one spot higher, talking about an item, or passing.  If everyone passes, the ordering is done.  The Challenge, Estimate, Override and the Relative Mass Valuation methods are variations on the ordering protocol.

Divide until Maximum Size or Less

The group decides on a maximum size for items (e.g. 1 person-day of effort).  Each item is discussed to determine if it is already that size or less.  If the item is larger than the maximum size, then the group breaks the item into sub-items and repeats the process with the sub-items.  This continues until all items are in the allowed size range.

Principles of Agile Estimation

Agile estimation techniques are collaborative.  All appropriate people are included in the process.  For example the whole Scrum team participates in estimating effort of Product Backlog Items.  Collaborative techniques are also designed so that it is impossible to blame someone for an incorrect estimate: there is no way to trace who estimated what.

Agile estimation techniques are designed to be fast (-er than traditional techniques) and deliberately trade off accuracy.  We are not trying to learn to predict the future… or get better at estimation. Instead, we recognize that estimation is a non-value added activity and minimize it as much as possible.

Most Agile estimation techniques use relative units.  This means that we don’t try to estimate dollars or days directly.  Instead, we use “points” or even qualitative labels and simply compare the items we are estimating to each other.  This takes advantage of the human capacity to compare things to each other and avoids our difficulty in comparing something to an abstract concept (such as dollars or days).

Check out my recent “Agile Planning in a Nutshell” article.

What Other Agile Estimation Methods Are There?  Please let me know in the comments and feel free to include a link!


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Pitfall of Scrum: Cancelled Sprint – Failure to Restart

Although a cancelled Sprint is rare, it can be tempting to try and wait until everything is “perfect” or “ready” before re-starting. Teams should immediately re-start after cancelling a Sprint. One team I heard of was doing two week Sprints, cancelled due to a major tool problem, and then waited three months for the vendor to fix the problem before going back to Sprinting. Instead, they should have used their creative problem-solving skills to find a way to continue delivering value and restarted their Sprints immediately.

The Scrum Guide puts Sprint cancellation under the authority of the Product Owner:

A Sprint can be cancelled before the Sprint time-box is over. Only the Product Owner has the authority to cancel the Sprint, although he or she may do so under influence from the stakeholders, the Development Team, or the Scrum Master.

It is important to note that older descriptions of Scrum will sometimes mention that the ScrumMaster or the Development Team can also cancel a Sprint. This is no longer part of the core definition of Scrum.

Cancelled Sprint Emotions

A cancelled Sprint can sometimes be emotionally challenging for a Scrum Team. There are three reasons for this difficulty:

  1. Cancelling a Sprint, particularly later on in the timebox means there’s a lot of work already in progress (and possibly done). The psychology of sunk costs comes into play: we’ve invested some much in the Sprint so far, let’s just keep going to see if we can “fix” it. Going against that impulse can be very difficult.
  2. A cancelled Sprint is an acknowledgement that the fundamental direction of the current Sprint is no longer the right thing to be doing. This can seem to be an insult to the team: why didn’t “you” get it right earlier? If there are certain people on the team who advocated strongly for the current set of work, they could take Sprint cancellation particularly hard.
  3. Cancelling a Sprint may require undoing technical work and may be complex. If team members have made changes that they are particularly proud of, they may resist undoing that work more than would be called for simply due to the time involved in undoing it.

Once people experience these emotional effects from a cancelled Sprint, they will want to be cautious to avoid them re-occuring. That sense of caution will lead people to make arguments to the effect of “let’s make sure when we start our next Sprint that we have everything right” or simply, “I don’t want to go through that again… we better get it right this time around.” In order for the ScrumMaster to avoid falling for these arguments, it is important for the ScrumMaster not to be a hands-on contributor to the work. In other words, to be emotionally detached from the work. Those arguments can be persuasive unless the ScrumMaster can remind the team about empiricism.  The ScrumMaster must always support the Product Owner if the product owner believes that a cancelled Sprint will lead to the best business outcomes.

Scrum is an empirical process that allows for “failure”. Of course, it probably helps to not call it that. Instead, a Scrum Team and the organization around it need to think of every Sprint as an experiment. There’s a good analogy here with the various stages of drug trials. When a company wants to research a new drug, the drug will go through various stages of experiments. The early stages of research are based on chemical reactions in the proverbial test tubes – laboratory experiments. Subsequent stages of research are often based on animal experiments. After that come human trials. At any stage if the drug in question is showing adverse effects outweighing the therapeutic effects, then the current stage is cancelled. Of course, the research done to that point is not a waste, but nor does it immediately result in a useful drug with net therapeutic effects. In Scrum, each Sprint is like a stage in the drug trials. If the work of the Sprint will not result in a net benefit, it only makes sense to cancel the work as soon as that information becomes obvious.

Waiting for Perfection

The pitfall, then, is that after a cancelled Sprint a team will feel pressure to wait until conditions are perfect before continuing on the next Sprint. Scrum does allow for the team to do a bit of a review of the reasons that the Sprint was cancelled, perhaps even to do a retrospective, and then start another Sprint planning meeting. The Sprint Planning meeting might be a bit longer than usual. The ScrumMaster does need to be sensitive to the needs of the team.

Cancelled Sprints and Synchronized Teams

One other factor may be a consideration: if the team is working with other teams on a larger-scale effort, there may be pressure to have all the teams with synchronized Sprints. For example, the Scaled Agile Framework emphasizes cadence and synchronization among multiple Scrum teams. In this case, a cancelled Sprint may mean that a team sits idle for a short time while they wait for the next synchronization point, as illustrated:

Cancelled Sprint in SAFe

This article is a follow-up article to the 24 Common Scrum Pitfalls written back in 2011.


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