In high school I tried to build a mass spectrometer. It didn't work - I couldn't get a high enough vacuum, and a few years later as a physics undergrad did I find that that was only one of several problems I had. It was fun to try though.

But I do know that the ionized particle has a charge, and that electron affects the overall mass, by about 1/1836 Dalton . That's 0.00054 Dalton, while the table lists masses down to even higher accuracy, like 71.03711 .

The example output gives a value down to 3 decimal digits, so at that precision there's a 50% chance that the electron mass will affect the result.

Isn't this problem therefore implicitly teaching an excessive trust in significant digits?

Now, I suspect that the mass spectrometers they use aren't that accurate. But it's bugging me now.

As mbreese wrote elsewhere here, I'm (clearly) reading too much into the problem. I don't think bioinformatics is the right field for me.