I mean I suppose if you played ONLY Izmail or whatever for 100 battles you'd know better, or the test would be better, but the problem is that there still are so many variables, its never going to be exact.
Like case in point, I've played on the weekend for 4 hours, not been uptiered ONCE, then 2 hours on a Monday evening and had EVERY battle be uptiered....
So maybe if you ONLY played a specific ship at a specific time of day every day... but still, it is NOT exact.
-Hapa