I am an IB student, and I want to major in psychology. However, I do not have biology as a subject. Should I give the AP exam in bio or psych if I want to get credits to most universities in USA?
You have enough classwork going on to get through your IB program. Focus on that. You can take biology once you get to college. It makes no sense at all for you to try to teach yourself the content of first year college biology just to take an AP exam in the hope that you might get academic credit for the exam score.
At this point many (perhaps most?) colleges who give credit for APs will also give credit for IB exams (most often for HL scores of 5/6/7)… Policies on giving credit for APs & IB vary a lot by college, but are usually on the website. Many colleges limit the number of credits towards graduation that you can get from AP/IB exams. There is also a difference between being exempted from an introductory level course and getting credit towards graduation.
what about economics in ib? should i take ap microecon as well? considering majoring in eco is also one of my options?
No.
The colleges don’t really like self study for AP’s.
Do what’s available at your site.
Taking AP tests will not “improve” your chances as an international student.
To echo the responses you already got and add another thought:
It’s not easy to take an AP exam on your own. You cannot sign up for AP exams like you’d sign up for the SATs. A school which administers the exam you want to take has to register you as a test-taker. Most schools only want to register their own students. (Add that the regular registration deadline for the May 2020 exams has already passed. It was November 15.)
Since selective universities limit the number of credits they award for high school work, it’s unlikely that you’d receive credits for both your IB and additional APs. Would you rather get AP credits instead of* IB credits?