To be honest, I effectively removed myself as a candidate by admitting I wanted a different role. Trading assistant is not the same as assistant trader, the former is more like "secretary" while the latter leads to becoming a full time trader.
Initial contact was made via email. I was given a small take home case to do which basically tests your basic knowledge of excel. The most complicated thing you have to do is know how to use a SUMIF function.
After that, the first phone interview consists of a few behavioral questions then mostly math problems
Honestly, even if I was looking to be an assistant and was offered this position, I wouldn't take it. There is no guarantee even if you get an offer you will keep a job since the first three months is a "trial period" after which they decide whether to keep you (also makes for an easy way to lay people off if they find they don't need additional assistants).
Questions were as follows (no pen, paper, calculator allowed)
1. Angle between hands on clock at 9:30 - I said 105 degrees. (they are three and a half hours apart since the hour hand would be at 9.5).
2. Odds of at least 2 heads in 4 even coin toss - I said 11/16 (16 possibilities 4c4 + 4c3 +4c2 = 1+4+6)
3. 15% of 135 - I said 20.25 (mental math trick 100*.15 + 30*.15 + 5*.15 = 15 + 4.5 + 0.75 = 20.25)
4. Odds a world series matchup (baseball) makes it to game 7 if even teams (50/50 chance) - I said 5/16 (odds of first 5 games ending in 3/2 are 5c3*2 = 20 / 32 possibilities = 5/8 chance, then odds of game 6 ending in 3/3 = 1/2 so 5/8*1/2 = 5/16)
5. If a bus starts with x people on it, 3/4 get off 7 get on at stop 1, same at stop 2, then again at stop 3, what is the minimum number of people who started on the bus? - I said 52 (let y = 1/4x, y mod 4 = 1 also z = .25(y + 7) mod 4 = 1, we see that z cannot be 1 since that would imply y is negative, so minimum value of z = 5. then y = 13, x =52.)