Ailment buffs were first introduced with the Dragons and Slayers (Arus) batch, which granted party-wide buffs of minor chances to inflict specified ailments. However I'm not sure most people understand how strong (weak, actually) these buffs can be. If you apply a bit of binomial probability (AP Stats ftw), it becomes easier to understand.

Ailment buff strengths are most commonly 10% or 15%, and occasionally 18%. These are the probabilities of a single attack resulting in a positive proc. The number of units alive on your squad are the number of attacks you have in a single turn. Also, these calculations are done without considering any ailment resistance from the enemy.

Units Alive|10% Buff|15% Buff|18% Buff :--|:--|:-- 6|47%|62%|70% 5|41%|56%|63% 4|34%|48%|55% 3|27%|39%|45% 2|19%|28%|33% 1|10%|15%|18%

Obviously, the less units alive, the less effective the buff; but the rate at which the buff becomes weaker also increases the more units you lose. For example, if you have an 18% injury buff, you only lose 7% chance of inflicting injury if you lose a single unit, but if you lose your fifth unit and have only one remaining, your chance of inflicting injury drops by 15%, more than double.

Also, some units (Torah and Magnazorda) have ailment buff LSs that couple with their BB/SBB ailment buffs to make combined probabilities of 20%, 25%, and 30% possible.

Units Alive|20% Buff|25% Buff|30% Buff :--|:--|:-- 6|74%|82%|88% 5|67%|76%|83% 4|59%|68%|76% 3|49%|58%|66% 2|36%|44%|51% 1|20%|25%|30%

7 star forms of Sefia and Kikuri combine ailment buffs with ailment proc chances on their own BB, and other, lesser used attacks (Edea 7's BB, Tora/Magnazorda 6's LS) have a 7% chance of inflicting an ailment, but I don't think those're worth calculation tables. Regardless, I hope you learned something new about ailment buffs today!