Use easy to remember number sequences

Daniele Catalanotto
Mar 18, 2022


A Service Design principle for better memorization

It's covid time. Here in Switzerland, the state offers each citizen some covid tests that you can do at home. Smart.

With the tests comes a little guide about how to use them. First, you should turn the Q-tip in each nosehole 15 times. Then put the Q-tip in a little plastic device. From which you can take 4 drops that you put on the test. And finally, you wait 15 minutes to see the result.

Did you notice something? The smart people that wrote the guide used an easy to remember number sequence 15-4-15. The number 15 comes back twice.

Would it change the validity of the test if you turned the Q-tip 10 times in your nosehole? I'm not sure. But it's easier to remember 15 because it's also the number of minutes you have to wait for the test to give you the result.

So when your team or users have to use number sequences, you can do the same thing:

Round the numbers up so that the sequence is easier to memorize.


Little side notes

  • This is the second draft of this Service Design Principle.
  • I was able to reduce the lengths of this principle by about 10.65% compared to the first version.
  • Once adapted, even more, this principle will be part of the book "Service Design Principles 201-300"
  • As always comments and feedback to improve this principle are welcome
  • If you have a personal story that goes in that direction it would also help if you share it 
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Patrick Marcelissen
May 9, 2022
Clear to read the message from this principle 
Daniele Catalanotto
Oct 31, 2022

The third draft of this Service Design Principle

In the middle of the pandemic, the Swiss state offers each citizen covid tests to do at home.

The tests come with a guide explaining how to use them. First, turn the Q-tip in each nosehole 15 times. Then put the Q-tip in a little plastic device. From it, take 4 drops that you put on the test. Finally, wait 15 minutes to get the result.

I’m not sure it changes much if you turn the Q-tip 10 times instead of 15 in your nose. But it’s easier to remember! Because 15 is also the number of minutes, you must wait for the test.

Let me ask you.

Is there a process where you could make things easier to remember by rounding the numbers?

Daniele’s notes

  • This is the third draft of this principle.
  • I’ve reduced the length of this principle by 29 % compared to the previous draft.
  • I’ve added a conclusion question to help the reader turn this principle into action.