Dear aspirant,

There is no criteria regarding number of attempt and age for appearing in ISI test for undergraduate courses. To get eligible for ISI Admission exam you must have a 3 year Bachelor's degree in Economics/ Mathematics/ Statistics/ Physics, or a B Stat degree from ISI, or a BE/ B Tech degree or any other qualification considered equivalent (such as AMIE). Candidates will have to appear for the written tests and subsequent interview.

Hope this information helped you.

All The Best!!