Board Thread:Skyrim/@comment-1401879-20130614233659/@comment-98.210.220.20-20130903050144

That multiplication doesn't make sense. That would mean stacking made your resist smaller, which is demonstrably not true. I think it's more like:

B=base resist

(B*1.11)^3

So, if your base resist is 1 it would be:

1*1.11=1.11

1.11*1.11=1.2321

1.2321*1.11=1.367631

Which would actually be better than being additive. So, I'd guess it's likely additive up to a certain cutoff point. I guess you could test this by putting on 10% resist gear, placing a rune trap, setting it off when you're near, counting the damage done, putting on another 10% resist, and trying again.