Tuesday, August 10, 2021

#RPGaDAY2021 Day 10 Advantage

RPGaDAY2021 Day 10

Going for another alt-word today. Plus it gives me the chance to talk about one of my favorite topics.

Day 10 Advantage

One of my favorite new mechanics with D&D 5e is the Advantage / Disadvantage ruling.  It is pretty simple really. A situation is in your favor, roll with Advantage, that is roll two d20s and keep the highest.  If a situation is against you then roll with Disadvantage; roll two d20s and take the lowest.   

It's not really revolutionary, but it is a nice quick way to adjudicate rulings and many rules use it.

Simply if you have advantage due to one condition and advantage on another one you still have only two d20s.  If you have advantage and disadvantage they cancel each other out. 

The thing that I like about it the most is the nice probability curves they generate. 

You might recall that prior to selling my soul to the dot com world I was a Statistics professor at the University of Illinois colleges of Education, then Medicine. I taught at the undergraduate and graduate levels for years.  I LOVE statistics.    

I knocked together some simple frequency graphs of rolling a d20 normally, with disadvantage, advantage, and with a simple +3.   These are chances of rolling the number (1 to 20) or higher on a d20.

The Data


The Graphs

The Graph

Rolls are on the X-Axis (1 - 20) and the Probability on the Y-Axis (0.0 - 1.0).  

The red line is our normal d20 roll. Blue is disadvantage (2d20, take lowest), yellow is Advantage (2d20, take highest), finally, the green is normal +3. 

Is it much?  Not really in the short term, but over 1000s of rolls over the last 7 years the effect has added up.   And it is always a lot of fun.  Especially when you are rolling and get two 20 (a 1 in 400 chance). Fun when you are rolling with advantage, but fantastic when you are rolling with disadvantage.

I have adapted it for use in my OSR games and it works great.  


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