Updated: Agile Estimation with the Bucket System

I have added a pdf download of this article about Agile Estimation with the Bucket System.  It’s just a handy, nicely-formatted document that can be used for quick reference.  It is now part of the materials I give out for my Certified ScrumMaster training classes.

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Agile Estimation with the Bucket System

Estimation – The Bucket System [pdf] – printable reference version of this article.

The “Bucket System” is a way to do estimation of large numbers of items with a small to medium sized group of people, and to do it quickly.  The Bucket System has the following qualities which make it particularly suitable for use in Agile environments:

  • It’s fast!  A couple hundred items can be estimated in as little time as one hour.
  • It’s collaborative.  Everyone in a group participates roughly equally.
  • It provides relative results not absolute estimates (points vs. hours).
  • The results are not traceable to individuals and so it encourages group accountability.
  • Works with teams to estimate effort or with stakeholders to estimate value.

BucketSystem3

The Bucket System of estimation works as follows:

  1. Set up the physical environment as per the diagram below.  Ensure that all the items to be estimated are written on cards.
  2. Choose an item at random from the collection.  Read it to the group.  Place it in the “8″ bucket.  This item is our first reference item.
  3. Choose another item at random from the collection.  Read it to the group.  The group discusses its relative position on the scale.  Once consensus has been reached, put the item in the appropriate bucket.
  4. Choose a third item at random and, after discussion and consensus is reached, place it in the appropriate bucket.
  5. If the random items have clearly skewed the scale towards one end or the other, re-scale the items (e.g. if the first item is actually very small and should be in the “1″ bucket).
  6. Divide and conquer.  Allocate all the remaining items equally to all the participants.  Each participant places items on the scale without discussion with other participants.   If a person has an item that they truly do not understand, then that item can be offered to someone else.
  7. Sanity check!  Everyone quietly reviews the items on the scale.  If a participant finds an item that they believe is out of place, they are welcome to bring it to the attention of the group.  The group then discusses it until consensus is reached and it is placed in one of the buckets.
  8. Write the bucket numbers on the cards so that the estimates are recorded.

Bucket SystemSome important points to consider:

  • Multiple items can be in the same bucket.
  • Items cannot be placed “between” buckets to represent a more precise estimate.
  • If the distribution of the items is skewed to either end of the scale, then during the sanity check step the group should also discuss if the items can and should be spread out more evenly along the scale.  If so, then the group does it collectively.
  • The facilitator should watch to make sure that no one moves items that have already been placed until the “sanity check” step.
  • The division of items among participants does not need to be exactly equal – don’t worry about “dealing” out the items.  Instead, just divide them up roughly.
  • If the “divide and conquer” stage has one or two people working very slowly through their items, it is acceptable to suggest that they share their remaining items with people who are already finished.
  • It is not acceptable for an individual to completely abstain from the process.  If someone desires to abstain, they should be counselled that this means they will not have any future say in the estimates.
  • During the “divide and conquer” stage it is critical that absolute silence is maintained.  In particular, there should be no bilateral discussion of items.  This is to protect the anonymity of individuals placing items as much as possible.

The Bucket System

 

The bucket system is a good alternative estimation method to try instead of Planning Poker.  It is much faster than Planning Poker and still gets reasonable results.

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The Planning Game – An Estimation Method for Agile Teams

The Planning Game [PDF] – printable reference.

Purpose: estimate the effort for User Stories (Product Backlog Items, Value Drivers)

Prerequisites: all items have a value estimate, each item is written on a separate note card, full team membership is known and available for planning, each team member has a set of planning game cards

Process:

  1. The team goes through all the items and chooses the one which has the lowest effort. Write the number “2″ on this card (usually in the bottom right corner).
  2. The team looks at the item with the highest value.
  3. Each team member thinks about how much effort the team will expend to fully complete all the work for the item. Comparing this work to the work effort for the smallest item, each team member selects a card that represents this relative effort. For example, if you think that it requires ten times the effort, you would select the “20″ card. It is not permissible to select two cards.
  4. Each team member places their selected card, face down, on the table. Once all team members have done this, turn the cards over.
  5. If all team members show the same value, then write the value on the item and go back to step three for the next item. (Or if there are no more items, then the process is complete.)
  6. The person with the highest and the lowest value cards both briefly explain why they voted the way they did. If there is a Product Owner present, this person can add any clarifications about the item.
  7. For any given item, if a person is highest or lowest more than once, then each explanation must include new information or reasoning.
  8. Once explanations are complete, the team members collect their cards and go back to step three.

Notes:
- it is extremely important that the voting for an item continues until all team members unanimously vote the same way (this way team members and outside stakeholders cannot blame any individual for “wrong” estimates)
- in Scrum, it is normal for the Product Owner to be present during this process, but not to participate in the voting
- in OpenAgile, it is acceptable for people serving as Growth Facilitators for a team to participate in the voting
- voting should not include extensive discussion
- if more than one person has the lowest or highest vote, usually just one person shares their reason in order to help the process move quickly
- the first few items will often take 10 or 15 rounds of voting before the team arrives at a unanimous vote
- later on, items may take just one or two rounds of voting to arrive at a unanimous decision
- some teams, where trust levels are high, will discard with the use of physical cards and just briefly discuss votes

The planning game is used at the start of a project with the full list of user stories. In this case, it is reasonable to expect the team to average two minutes per user story, and an appropriate amount of time needs to be set aside to accommodate going through the whole list.

The Planning Game is also used any time that there is a change in the list of user stories: re-ordering, adding or removing user stories, or changes to a single user story. When such a change happens, the team can re-estimate any user story in the whole list. When starting a Cycle or Sprint or Iteration, all the user stories in the list should have up-to-date estimates so that estimation work is avoided in the Cycle planning meeting.

Finally, the team can decide to re-estimate any user stories at any time for any reason. However, it is important for team members to remember that estimation is non-value-added work and the time spent on it should be minimized.

NOTE: The Planning Game is described as Planning Poker on wikipedia.  The version described there has some minor variations from this version.

A closely related method of Agile Estimation is the Bucket System.

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