The percentage of condition an item is repaired is determined by your repair skill. The higher your repair skill, the better the results from repairing.
The same goes for items you create when crafting. The higher your repair skill, the better the starting condition of a crafted item.
At least that is how it works in FO3.
This would seem to make sense...
I'm not entirely certain if the game still does it the same way, either, but I'm hoping that this is the case.
Thanks for the answer, though! Definitely helps me out!