Noob question :) Strength boosts?

I have seen some people mention that they don't like to use militia and I don't usually produce very many militia in my games however, I can't help but notice the strength boost in hill territories.

So the noob question is: Are the boosts simply a straight add or subtract to whatever the base stats of the applicable units are?

For example, the base stats of a Level 1 Militia are:

Infantry Attack = 1.5

Infantry Defense = 2.3

Armor Attack = 0.3

Armor Defense = 0.5

Air Defense = 0.7

But in hill territories, if you add 75% to the base stats, the Level 1 Militia stats are:

Infantry Attack = 2.625 (Level 1 Infantry is 2.0)

Infantry Defense = 4.025 (Level 1 Infantry is 3.0)

Armor Attack = 0.525 (Admittedly Infantry are better against armored units)

Armor Defense = 0.875

Air Defense = 1.225

I also noticed a thread in the forums regarding Commandos - so in mountains Commandos get a 100% strength boost bringing their Infantry Attack stat to 20.0, and Armor Attack stat to 10.0?

So yeah, the question is just if the strength boost is a straight add/subtract or is there some algorithm that takes the various strength boost percentages into consideration?

Thanks