How To: Sizing and Estimation Game

The Zoo Game

When starting out with teams I like to facilitate an exercise called “The Zoo Game” to bring relative sizing and estimation to life.  It is a practical exercise that is run with the whole team together.

Getting started

If the team are located in the same office, then you will need the following equipment

Large post-it notes with XS, Small, Medium, Large, XL

Large Post-it notes with 0,0.5,1,2,3,5,8,13, 20 written on them.

Medium Post-it notes with the following animals written on them or use pictures of the animals for reference.

  • Flea
  • Bee
  • Mouse
  • Rabbit
  • Cat
  • Dog
  • Lion
  • Bear
  • Giraffe
  • Whale

A selection of stories from the team backlog of differing sizes.

If the team are distributed or working from home then follow the above instructions but use Miro or Mural to allow the team to interact.

Why we use this game

When teams start to work together they often equate points to either hours or days.  This can then become confusing for teams when something takes a few minutes and this can in turn lead to confusing scales which makes it hard for teams to estimate.  Jira has now allowed for decimal points in sizing which is adding fuel to the flames.  This exercise should help raise things up a little. 

With relative estimation, the unit that you use to compare items doesn’t really matter as long it is agreed with the team and the team are able to identify how big an item is in comparison to other items that are being estimated.  This will become apparent during the game.

We run through 2 sizing methods in this exercise to show the differing levels of granularity that each can bring.  T-Shirt Sizing and the Fibonacci sequence is used.

The outline

Place the Large T-Shirt sizes on to the wall, mix up the animals and place them on the wall nearby.

We kick off by explaining the outline of the exercise.  We are firstly looking to estimate the size of our group of animals relative to each other using T-Shirt Sizes.  Ask one person to kick the exercise off by picking the animal that they think sits in the middle value (Medium).  Ask each person to add one animal from the list to the scale reminding them that they can move items up or down but only if they discuss their thoughts with the team and gain agreement.

You should begin to see conversations or questions begin to emerge around what scale is being used.  Is it height? is it weight? Or even length has been used in one exercise.  As long as the team decide which scale they want to use during the exercise it should run smoothly.

Once the exercise is complete and the animals have been added to each of the sections ask the team for their observations.  They should see that each size acts like a “Bucket” where there can be a noticeable difference in size between animals.  i.e. the flea to the bee.  Point out that this is where we need to become a little more granular in sizing to improve our estimation. 

Move on to the Fibonacci sequence and perform the exercise using the same animals again.  The team can use the same agreed sizing scale.  As they move through the exercise they will see that using the Fibonacci sequence allows a more granular.

Once the animals have been populated, discuss the team’s observations and ask them if they could see themselves sizing in this way.  

Move on to populating their actual work items again, agreeing the scale while trying to avoid hours or days.

Using this in the real world

Once you have completed the animal sizing and populated the items from your backlog to the scale it is time to put this exercise to good use.

You can use the scale at your next refinement session to compare items in the backlog against items of the scale.  The scale is fluid, you may find that items move up or down as we begin to learn and unearth more detail.  After a few Sprints the team will begin to find enough muscle memory that they can move on from the scale and use it as a reference when needed.

Published by The Daily Scrum

A CSP, CSM, CSPO who lives and works in Glasgow, UK.

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