I really need to clear one detail about this, because of scripts I work on, some spells undergo calculations to determine final chance of effect. For example, when creature cast Symbol Stun and want to hit target where chance is highest Stun effect will apply, you have to take both Magic resistance and Save vs Spell into calculation.
Now - exact question is - Saving Throw value of 2, is exactly how much percent of chance to save, 5% or 10% ?
Assuming, that spell cast do not have Save penality.
I tested (let creature be hit hundreds of time with weapon which apply some effect - probability 100%, but with save penality at 0), at creature which have Saving Throw value of 1, and 20. So I can 100% say, on 1 it will always save, on 20 it will always fail.
But I need to know values between.
Butt-kicking for goodness!