What hell is this drop rate

[Rednaxus1]

For some reason I have killed 11 black ox Beatles according to the wiki there is 50% chance that I will get a horn and yet I have gotten none I watched some YouTube and some people get the horn on their first try but these videos were 2 years ago so what the hell happened.

[iMiAMi2014]

Nothing happened (except for the appearance of the Advanced Loot Table, but this does not matter in this case). It's just that 11 kills is not a very large sample, I also encountered a series of 10-15 kills without horn drop.