[wat10000]

Sorry, but this annoys me. The claim might be false if I had made it after seeing your screenshot. But you don't know what I've seen in my life up to that point. The claim that all calculators are infallible would be false, but that's not the claim I made.

When a personal experience is cited, a valid counterargument would be "your experience is not representative," not "you are incorrect about your own experience."

[stavros]

Well if you haven't seen enough calculators to see one that can't add, a very common issue with floating point arithmetic on computers, you shouldn't offer your experience as an argument for anything other than that you haven't seen enough calculators.

[wat10000]

How many calculators do I need to have seen in order to make the claim that there are many calculators which are essentially 100% reliable?

Note that I am referring to actual physical calculators, not calculator apps on computers.

[stavros]

Well, to make the claim you actually made, which is that you haven't seen a single calculator that was wrong, anywhere from zero to all of them. It's just that the "zero" end of that spectrum doesn't really tell us anything about calculators.

[wat10000]

When was the last time you saw an actual calculator (not an app) give a wrong (not merely rounded) answer?