Originally Posted by fallenj
Kind of wonder where you get these percents at for advantage/disadvantage. I could be wrong but isn't the rule roll a additional d20 an high goes to advantage an low goes to disadvantage. If you have both it's nullified except for halflings that can reroll 1s.

If this is the case bless an the other spell will have more value than you say since the percent is not 100% accurate.

Statistical modeling is where understanding the effectiveness of Advantage/Disadvantage comes from.


The chances of rolling a 10 or greater on a D20 are 55%. Every single number has a 5% chance to come up with a single roll.
If you have disadvantage, where you roll two d20 and take the lower, the chances of rolling a 10 or greater drop to 30.3%
If you have advantage, the chances of rolling a 10 or greater increases to 79.8%.

If anything, the OP's use of 10% increase for advantage is understating things.