Type Attacks

I've been wondering how Type Attacks work. Obviously there's some sort of multiplier for a correct type attack, but what is it? Is it 1.5x or 2x? I've been wondering this for a while and wonder if anyone else might know the answer.

I think its x1.5 but i’m still trying to figure this out. Also i know for sure that if you attack a rock type with a rock type attack the result dmg will be the same as if it was a normal attack.

Not a perfect answer but i hope it helped.