When I was in Sweden, the one hospital I visited had an automated coffee machine that made a variety of drinks. In getting a cup of coffee, or trying, I found an example of everyday error proofing.
When I first put the mug under the spout and pressed the coffee button, nothing happened. I thought the machine was broken, so I tried its twin sitting to the right. Same problem. Then, I realized, I had been outsmarted by the error proofing.
Based on the visual of the machine, I set the mug in what I thought was the correct place, as shown below.
As it turns out, that's actually the drain and the correct place to set the cup is above on the black holder that juts out from the machine.
The machine was mistake proofed, as it sensed that there was no mug sitting on the correct spot. If there had been no mug at all, that would have created a big mess. Having a mug sitting where I had it might have made a little mess, as hot liquid would have splashed through the black holder above the mug. Maybe they could have had a sensor on the bottom grate, but that adds cost (well, so did the mistake proofing logic).
This is a mistake you don't make twice, once you learn how the machine works.
Below is a picture showing where the mug should have gone (above the original mug):
What do you think — clever error proofing or overly engineered?
You could also argue, maybe, that it should have been more visually clear where to put the mug… then maybe error proofing wouldn't have been necessary. Maybe I would have been more likely to get the right spot if the drain had been black and the mug holder had silver?
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