An interviewer could ask you how you react to criticism and listen to you try to impress him by going on and on about how well you respond to having your work challenged... or he might just interject a little friction into the interview and see for himself how you react. Do you fold even if you are correct? Do you simply resist? Do you think it through? There is almost nothing that good engineers get more of during their careers than criticism. It is the basis for disaster and error prevention as well as potential product enhancement. Of course, it is usually called 'constructive criticism' or a 'design review,' and in a good work environment it IS done in a positive manner and without blame. But it can still be challenging to be critiqued, even politely. Are you mature enough to handle it? You want your answer to acknowledge the possibility that you could be wrong while not ceding the field until you know more.
With a question like this, you need more information to know whether you were actually wrong at all, whether you should diplomatically defend your answer and allow the interviewer to save face by saying that you think it was correct, but you will go back and take another look; or whether you really DID have a gap in your knowledge. In that case, you might thank the interviewer for correcting you and wryly point out that you still have a lot to learn about the subject.
