» Fri Nov 27, 2015 3:22 am
It is a weighted random system.
Weighted in sense game text specifically tells us that lower defense ratio, not total number is what matters. E.g. Defense 20 vs 200 is meaningless - one is not stronger than another per se. The ratio game cares about for whatever weighted probability of attack is your food+water vs defense ratio.
If you have 240 food+water (easily achievable via 5 large ind. water purifiers and some crops) and 200 defense, you ratio is weak compared to 10 food+watee vs 20 defense.
No one knows the for ula and how much it skews the weighted chance but unkess game text is flat out wrong, it tells us chance of being attacked is reduced by greater defense ratio.
But since it is random, and we all know how bad some "RNG" systems are, many players report hardly ever being attack and some complain about too many, constant attacks.
I maintain a minimum 1:2 ratio - double defense vs my food+water and I am still attacked reasonable number of times. Not super common but not uncommon. Enough times that i really detest the weak warning system we get with easy to miss message and misc quest insertion with no real alert prompt, which I suspect is also buggy and doesnt give popup message always either.
If you want to experience attacks personally, build up your settlements and just play - regardless how strong the defense ratio is, I believe based on my xp, that raiders will attack what seems prosperois. They want resources, they attack resources. So even sanctuary, my most heavily defended settlement, is attacked a good number of times and in common frequency because it is also my gigantic adhesive factory.
I've also noted that type of mob that attacks is random but influenced by what quests you've done in sense of what mobs you've met. I am such a settlement sim player that I didnt do much main or side story quests like for BoS, and just explored for junk and cleared repeated same locations as loot/mobs respawned. So I did not meet any synths for a long time, and during that period while I was attacked aa good number of times, it never, ever included synths.
This could just seem sheer random chance, but it does seem a big coincidence I was attacked 10+ times without ever seeing synths, then I finally encountered synths for first time in a mission, and then suddenly my settlement attacks started including synths.
Last - i have encountered good chunk, at lesst 70% of my attacks when just fast traveling. I arrive and eithee statt hearing shots, or the alarm siren starts blaring. Build one of those at each settlement btw, very handy and useful.