100 Things You Should Know About People: #35 — People Make Mistakes

Example error message: This error should not occurI used to collect computer error messages. It was kind of a hobby. I’ve got a great collection of them, some of them going back to the old character based computer screens. Most of them are not error messages that were trying to be humorous. Most of them were written by computer programmers that were trying to explain what was going wrong. But many of them end up being quite funny (unless you are the one who got the message in the middle of trying to do something important. Then nothing seems funny). My favorite was from a company in Texas. When there was a “fatal” error, meaning the system was going to crash, a message came up that said, “Shut er down Henry, she’s spewin’ up mud!”

Error messages are probably the part of a software program that gets the least amount of time and energy, and maybe that is appropriate. After all, the best error message is no error message (meaning that the system is designed so that no one makes errors). But when something goes wrong it is important that people know what to do about it.

The reality is that something always goes wrong. People make mistakes. Whether the user makes a mistake in working with a computer, or a company that makes a mistake by releasing software that has too many errors, or a designer designs something that is unusable because he or she doesn’t understand what the user needs to do. Everyone makes mistakes. So here is my list of important things to consider about people making mistakes:

Think ahead about what the likely mistakes are — Figure out as much as you can about what kinds of mistakes people are going to make when they use whatever it is you have created. And then change your design before it goes out so that those mistakes won’t be made.
Create a prototype of whatever it is you have and then get real people to use it so you can see what the errors are likely to be.
Test your prototype with users (usability testing).
Write error messages in plain language. If you are creating a message to show someone or play audio to someone about a mistake they made, tell them the following:

  • that an error has been made
  • what the error is
  • how they can correct it
  • where to go to get more help in fixing the error

Use active voice and be direct. Instead of saying: “Before the invoice can be paid it is necessary that the invoice payment be earlier than the invoice create date”. Say instead, “Enter an invoice payment date that is BEFORE the invoice create date.”

Need it to be error-proof? It is very difficult to create a “system” that is free of all errors, and that guarantees that people won’t make mistakes. In fact it is impossible.  Ask the people at 3-mile island, or Chernobyl or British Petroleum. The more costly errors are, the more you need to avoid them. The more you need to avoid them the more expensive it is to design the system. If it is critical that people not make mistakes (i.e., you are a nuclear power plant, or an oil rig, or a medical device), then be prepared. You will have to test twice or three times more, and you will have to train two or three times more. It is really expensive to try and design a fail-safe system. And realize you never will fully succeed.

It’s just the way we are. We make mistakes!

If you have some favorite error messages that you have seen, consider sending them to me and I will add them to my collection.


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