Going to respectfully disagree with Aaron
I think it should be, ultimately, down to your own circumstance.
I tutored Methods & Specialist this year and have (subsequently) met students of a lot of different calibres.
Some of them started off the year with wonderful fundamentals, but I want to hone in on a specific example, someone who repeated Methods after a pretty below expectation performance in 2015 (he got ~25 raw).
This year? On the latest mock exam (2015 VCAA) he did better than my own score last year and is 'technically' on track for a 47 raw.
The difference to his ATAR? (28 --> 49+ which is a solid 20+ aggregate points considering Maths is his best subject).
Thinking about it, that's the same difference between an 87 and a 95, or the difference between a 77 and a 90. Basically, easily the difference between getting the course that you've dreamed of and missing the cut by a huge gap. Granted, the exam hasn't even been sat yet and I have no way of telling what his end study score will be (can confidently say he'll 40+, which by any margins is a 15+ aggregate boost).
However, for every success story you hear ^^ you'll hear a myriad of people increasing their study scores by 1-3 or in some rare cases, spend an extra year and get a lower score.
Bottom line i'd say is:
If you
think you completely bombed the exam due to exam anxiety and
not lack of preparation and you get a study score of below 40, it can make sense to redo.
If you got 40+, bombed the exam but you know part of it may be because you didn't study hard enough or some questions just stumped you, then it's probably not worth it.
Regardless, if you're planning on redoing, i'd suggest reevaluating the
reasons behind why you didn't perform so well. Is it because you didn't study hard enough? Is it because you were unaccustomed to something, was it just pure bad luck (be honest with yourself, because redoing can only fix some of these factors)?
I think Brenden has a point in the sense that, unless you're
certain that you'd do a whole heap better and have the determination to see things through (it is not an easy task), there's probably no point.
But it is certainly possible