What Advantage and Disadvantage Actually Do

I became curious about what the actual effects of Advantage (best of two) and Disadvantage (worst of two) are on d20 rolls, so I plotted out the possibilities: The 400 Rolls comes from the 20X20 matrix used for the Advantage/Disadvantage calculations, and gives an ideal distribution of 20 occurrences for each value when rolling a single die.  The plot shows the relative likelihood of rolling a given number or better under the three conditions (I felt that this was the simplest way to show the effects).  It is interesting to see how crippling Disadvantage is at the top end.

Thats a post regarding a specific game's mechanics, it's not really a topic for this forum (which is about roll20). But while the conversation is here... Yes, advantage has a crippling effect on low rolls, and disadvantage a crippling effect on high rolls - which is why I think so many Apocalypse World games shouldnt be rushing to adopt Adv/Dis instead of +/-1. In those systems (which use 2d6, not 2d20) the roll distribution is very important, and drastically cutting down one side of the roll has an outsize effect, especially for people with high stats.