My brother appeared for the interview last year, so I think I can answer your question.

The panelists will evaluate your ability to explain new questions. They might even ask you to solve the questions on the board. You must be clear about your choice of ISI Kolkata as you will be asked the reason for the same during the interview.

Expect questions on topics such as Calculus, Geometry, Combinatorics, and Probability. Keep your basics clear, know the definitions, and practice solving problems based on the definitions.

Just keep practicing, be confident and give your best shot at the interview.

Some of my friends took admission to ISI Kolkata for their bachelor's courses. Here are a few of their tips which you can follow while you prepare yourself at home.

• Lay emphasis on Mathematics concepts like Number Theory, Combinatorics, etc. from a standard book, like Excursion.
• Try to Solve a set of problems daily from the Test of maths at 10+2 level.
• Solve a lot of MCQs from JEE books which are easily available both offline and online.
• Learn calculus at an advanced level from the book - I.A. Maron, etc.
• Revise and fine-tune whatever you have learned till now. Take routine tests to keep a check on your preparation.

Overall, home preparation is quite simple if you want to score well enough for ISI Kolkata. Follow the important points and practice each and everything as much as you can. Also, you can always take help from your seniors who have gone through similar exams.

ISI Kolkata and ISI Bengaluru do not offer BSc (Hons) program. ISI Kolkata offers B.Stat and ISI Bengaluru offers B.Math.

Also, you can only apply for one course at a time because it is seen that all the exams for admissions in the Undergraduate, Postgraduate, Diploma, and JRF courses are held on one single day. It is usually held on the second Sunday of May every year. However, the exam for the course applied jointly by ISI Kolkata, IIT Kharagpur, and IIM Kolkata is usually held in the month of February.

Other than that, for all the courses of ISI, the exam is held on that single day itself and also has the same timings. The morning objective type test is usually conducted from 10:30-12:30 pm and the afternoon session subjective type test is conducted from 2:00-4:00 pm.

So you can only opt for one single exam. 

According to some of my friends from ISI Kolkata said it does offer undergraduate courses B.Stat or B.Math. Let me tell you some courses in detail for better insight.

Indian Statistical Institute offers the following two bachelor programs:

3-year B Stat (Honors):

• The criterion for this is you require successful completion of Higher Secondary (10+2) or equivalent with Mathematics and English as subjects.
• You will get a Stipend Rs.3000/- per month (Offered at Kolkata).

3-year B Math (Honors):

• The criterion for this is you require successful completion of Higher Secondary (10+2) or equivalent with Mathematics and English as subjects.
• Stipend Rs.3000/- per month (Offered at Bangalore).

Therefore, according to my friends, apart from these two undergraduate courses, ISI does not offer any other Bachelor Programs.

There is no doubt that ISI is an extremely and highly reputed institution. By any chance, if you are not left with any other alternative then it is worth waiting for ISI Kolkata.

• If you are planning for a master’s here, ISI Kolkata is a good choice.
• However, for a bachelor’s degree, you are advised to wait for a maximum of one year and not more than that under any circumstances. 
• It will be preferred if you go to other colleges.
• If you want to get a master's degree from ISI, I would recommend working throughout these two years while studying. 
• Do not just sit idle and do nothing as it doesn't look good on a resume. 
• Any work experience will be preferable to sitting at home.

If you are pursuing a bachelor's degree, study hard for one year, do nothing else, and ensure that you are accepted at the end of the year. Just to be safe, look into other colleges in India that specialize in mathematical sciences, such as CMI, Delhi School of Economics, IISc, and IIT.

If you are going for a Master’s degree just for the sake of getting good pay, then don't, it'll be a waste of your 2 precious years. Let me give you an overview: 

• M.Tech will not fetch you a 6-digit salary in an instant unless you are placed in a top company like Google. 
• If you're interested in going for M.Tech in CS then plan ahead- see what is asked in the ISI exam. You will find that it's mostly the B.Sc level Math.

If you are in Kolkata, then definitely go to ISI. There's a bookstore behind the college, it has a Math book especially for the ISI entrance test. You may buy and prep from that. 

Both the above-mentioned options are excellent to be considered. The IIMs prepares you to manage people and processes, whereas the ISI prepares you to be excellent quants.

Many IIM graduates work as quantitative analysts, they get the highest-paying jobs. If the ISI course is more appropriate, you could take the Bachelor of Statistics course. Quantitative analysts, on the other hand, tend to wear out soon, due to heavy workload.

An IIM education provides you with a broad perspective on management as well as access to a large alumni network. So, if you want to work your way up the corporate ladder, an IIM would be a better option. At the end of the day, it's up to you to decide where your priorities lie.