Post It Note Estimation is a great way to demonstrate relative estimation. Human beings are notoriously bad at estimating how long tasks will take in days, hours and minutes - and the greater the difference in task complexity, the worse we become at estimating! Relative estimation means we estimate a task relative to the size of another known task. Let's take a look at this post it note activity to learn more:
- Flip Chart
- Square Size Post-It
- Rectangle Size Post-It
- A5 Size Post-it
- A4 Paper
- Ask everyone to write down on a single post it an estimation as to how many post it notes they think it would take to fill up the whole piece of flip chart paper. Give them 1 minute to do this and ensure they do this on their own (no discussing their estimates with others as you want to avoid any anchoring bias). This needs to be done with the square size post it note.
- Ask the group to stick their estimates onto the flip chart for everyone to see, then arrange the lowest estimate at the bottom and the highest at the top.
- Use a marker to divide the flip chart in half, then divide one of the halves in half again to create two quarters.
- Ask how long they think they would need to all come to an agreement on one estimate. Let them discuss this for a few minutes.
- Explain you will now get everyone in the room to agree on one estimate in under 60 seconds.
- Give the square post it note a value of 1. Ask them to estimate how many square post it notes fit into the rectangle post it note. They will say 2, then write 2 on the rectangle post it.
- Ask them how many of the value 2 post it’s are needed to fill the A5 size post it. You will hear 2 and 3, this is where you explain you always round up, so if it is more than 2 then you always go with 3. “You never want to overfill the bucket” Write the value of 6 on the A5 post it (3 x value 2 post its)
- You then ask how many of the 6 value post it notes are needed to fill the A4 size paper, this is 2 again so this means the A4 paper is equal to a value of 12.
- Ask how many of the 12 value paper fill the quarter of the flip chart you previously drew up, this is 2, so naturally 24 for the quarter.
- Repeat for half the flip chart and then the whole flip chart and you will have a total of 96.
- Take a few minutes to see how varied the answers are in comparison to the estimate of 96 which they have all agreed.
- The correct answer is actually 80.
- Explain that humans are known to be very bad at estimating size, when it is anything more than 2 or 3 times as big or small as something else. This is why it’s always important to relatively estimate. It also shows how quickly you can get a large group to agree on an estimate without debating for too long.
How can you start using relative estimation every day as a group?How much time do you spend debating size of work within your team?
Always hold up the existing size next to the one you are asking the team to estimate. Once they have given the new size a value based on the old size, write this onto the post it note or paper to avoid them having to remember and recalculate each time.For example on the A4 paper would have written 12 so when you hold this up next to the quarter split on the flip chart then they can quickly say 2 then calculate 2 x 12 value to get to 24.This is a powerful quick exercise to help teams remember the importance of comparing pieces of work to other work being planned and to pieces of work previously done.Kudos to Matt Roadnight for first showing me this fab exercise.