I'm hoping someone can help us resolve this. A family member encountered the following grammar question on a test that would help qualify her to apply for a promotion:

Either you or I are mistaken.

Either you or I am mistaken.

She chose the first sentence and was told that it was incorrect, disqualifying her to compete for the promotion. Some of us think she was correct in that both sentences seem to be grammatically correct, others think she might have been correct due to common usage, and others think she was incorrect due to precedence of the closest pronoun. Some of us are just plain confused.

Can anyone help us figure out which sentence is grammatically correct? If the supervisor who graded the qualifying test was wrong, she may be eligible to reapply.

Thanks in advance.
Sorry, I don't have good news.

When you have an "either X or Y" you make the verb agree with what is in the Y position. If you have an I, we tend to put the "I" second, and so therefore we use "am."

Here's one reference .

If you think you can argue that she was correct based on "common usage," go for it - because you will certainly hear the "are" version.
That has surprised me, "either you or I are mistaken" definately sounds more natural!

Although I guess I would be more likely to say "one of us is mistaken".
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Thanks Grammar Geek! It feels better just to know, although she might still pursue the common usage angle.
Just out of curiosity. What job promotion could possibly hinge on being able to choose Either you or I am ...? English teacher?

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 A Cornish Pasty's reply was promoted to an answer.
A Cornish PastyAlthough I guess I would be more likely to say "one of us is mistaken".

Either you or I is mistaken is correct

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