I love when people say “I don’t know” confidently.
Unfortunately, this happens all too infrequent. Usually when someone asks a question, they don’t know what the right answer is (which is why they’re asking, duh). What this means is that regardless of whether you answer correct or not, your answer will usually be accepted by the other person.
We tend to reward people who give us answers, regardless of whether or not the answers are any good. Say you don’t know, feel stupid and you get a follow-up question. Or give your best guess with enough confidence and move on (most of the time, because the other person can’t tell you’re “bluffing”).
What I’m trying to say, I understand why people try give answers even when they really “don’t know”. What I wish is that more people understood that saying “I don’t know” is better for all parties.
If you have an answer to every question, people will gradually start to discount everything you say because they don’t know what’s inside and what’s outside your circle of competence. If on average you’re right half of the time, your answers will be valued at 0.5 - both your good and bad answers. Choosing to say I don’t know when that is actually the case, means your other answers has a higher value.
There are few ways to add more trust than to admit that you don’t have all the answers. Say you don’t know, and say it confidently. And people will trust everything else you say more.