If you’re going through a technical interview, Qualification exam for a PhD, talking to your boss, etc. there are different ways to say “I don’t know,” and you should probably use them more often than the bare “I don’t know.”
To be clear, if you don’t know something technical, do not try to bullshit your way through: say you don’t know. You cannot know everything. Also ask questions. More often than not, if you don’t know something that someone is trying to see if you know/get an actual answer and you don’t know the answer, you should answer in one of the following ways:
- I don’t know but someone does and this is where one would find/derive that information
- I don’t know and no one does but this is how one might discover the answer
- I don’t know and no one does and this is why it’s impossible to know Given a question there is exactly one correct way to say you don’t know. There’s a hidden (worse) way where you say that you also don’t know which category the question falls under.
Note, also, that if the question is a simple yes/no “are you familiar with X?”, don’t over-apply this advice, just say “no.”