IQR = interquartile range
in uni generally first years take quantitative methods which is extremely easy stats. no calculus involved, and 1/3 of the course is hypothesis testing. dead easy stuff.
usually that's where MOST people finish in terms of doing statistics units.
after quantitative methods, i then did regression modelling, which is a mandatory subject for actuary/finance students. no amount of high-school maths will prepare you for this because it doesn't NEED high-school maths, it's an extremely abstract statistics unit which had a midsemester failure rate of 90%.
then comes weird statistics courses like stochastic modelling, where you better prey your calculus is stellar, orelse failure is ensured.
also 90% of the reason why uni's put maths as prereqs is because calculus tends to be involved. essentially every science field uses it, not to mention actuary/economics/fianance. the only subjects that DON'T use calculus i would say would be arts, law and music.