ISI Kolkata does not provide a B.Math program. The majority of B.Stat students return for M.Stat while some people join CMI, TIFR, IIM, and other such organizations. 

M.Stat employees earn an average of 16–17 LPA, and many of them attend prestigious US graduate institutions. There are no fees for the entire program, and a stipend is provided. So, if you're looking for a career here, your future is bright.

ISI Kolkata is considered to be a good institute for B.Stats. It accepts admission purely on the basis of the entrance exam and the interview. The minimum eligibility criteria for the entrance is 70% in class 12th boards. 

The selection process will be finalized upon your performance in the entrance exam and the interview session. With this score, you will be able to pass through the cutoff but you must have an exemplary performance during the interview session.

Taking a course at IIT is just as difficult and demanding as pursuing a B.Stat course at ISI. They are whatever you choose to do with your life, whether you like mathematics/statistics enough to spend three years learning statistics (and a little math) and statistics solely at ISI, or you believe you are skilled in another subject that has a good course at one of the numerous IITs.

It depends totally on where you want to be. Furthermore, even if you prepare for college X, there is no guarantee that you will be accepted. As a result, keeping colleges Y and Z in mind as a backup is always a good idea.

Only you can decide which option is preferable for you and what you want. 

There are three sections in the entrance exam and the level of maths is the same as what you studied in your 12th. The exam follows the pattern of most high school mathematics competitions (RMO, INMO, etc).

The three sections of the Entrance Exam consist of MCQ, A Subjective Test, and an Interview.

The books you must know are:

1. Problem Solving Strategies by Engel Arthur
2. Test of Mathematics at the 10 + 2 level, Indian Statistical Institute, Published by Affiliated East-West Press Pvt. Ltd.
3. Challenge and Thrill of Pre-College Mathematics by B. J. Venkatachala

You should complete these all and do previous year’s papers of ISI/CMI RMO, INMO and IMO.

For Interview:

• Once you crack the exam, the interview part won’t be that difficult.
• Answer the questions confidently and honestly.
• The entrance exam of ISI is not easy and also there are only a few seats for B.Stat. 
• You have to prepare well.

Do not overthink and do your preparation well. This will help you a lot. Be calm and try to think of cracking the exam and the latter part would be an easy task for you.

The path you want to get into is a very dangerous one and it can totally spoil your career without you being able to do anything for it. 

ISI, B.Stat is a very famous course and is known for the entrance paper which is considered very tough by all those appearing in it. The course is tough because the student who is above the cutoff receives a huge financial help from the government covering the major portion of the tuition fee. Apart from this after the entrance exam the candidate can be certain of a well paid job one he/she completes the course and is awarded with the degree.

It gets difficult for the selections if there’s a year gap as lower age students are preferred and in your case there's a two year gap so the chances reduce even more. It would be very risky to change your college again and could cost some harm in your career.

Both B.Stat and B.Math are different courses being offered at different campuses at ISI Kolkata and ISI Bangalore respectively. There are only a few common subjects in both courses. 

The choice ultimately depends on your choice and interest. You can go through the syllabus of both courses and understand the topics. Find whichever interests you, you can choose to be research-oriented like B.math students or go for M.stat or other courses, if you choose so.

You can apply for only 1 course because the institute conducts the entrance of both courses at the same time and day. You will be able to appear for only one of them.

The required prerequisite for doing a B.Stat at Asutose College is 50% in the 12th standard. Having Statistics/Mathematics in your 10+2 is mandatory.

Students who have passed the 10+2 or equivalent examination and have also passed the English test with full marks of not less than 100 are eligible to apply.

If you have a lapse of more than 3 years from the year of passing the previous qualifying examination or the cessation of a recognized regular Course of Study after passing the previous qualifying test, then you are not eligible to apply.

To determine eligibility for admission to the Honors Course, add the marks in the top four subjects. Marks obtained in mandatory Environmental Education/Studies, on the other hand, will not be factored into the final grade. You must have a minimum of 50% in aggregate and pass Mathematics.

Students from the SC/ST or OBC categories need to have a minimum of 40% in the previous qualifying examination.

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.