Skill Check Probabilities

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Zhym
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Skill Check Probabilities

#1 Post by Zhym »

I got curious about the probabilities of success using the skill check system described by ToniXX and used in some of the games here. Here's a chart of the likelihood of success for each attribute value under a d20, 2d6, 3d6, 4d6, and 5d6 ability check:
Ability Checks.png
Ability Checks.png (116.58 KiB) Viewed 2650 times
For example, a character with an attribute of 12 will always succeed against a 2d6 check (obviously), has a 60% chance of passing a d20 check, and only about a 10% chance of succeeding against a 5d6 check.

If you want the raw numbers:
Screen Shot 2015-05-31 at 2.22.37 PM.png
Screen Shot 2015-05-31 at 2.22.37 PM.png (40.7 KiB) Viewed 2650 times
The professors in my Ph.D. program would give me grief for using a line chart to represent discrete probabilities, and I feel a little unclean for doing so, but it's a lot easier to read than a clustered bar chart.

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onlyme
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Re: Skill Check Probabilities

#2 Post by onlyme »

Charts work for me... I did the same thing a few times based on probability of winning a fight at various ACs.
Dandelion - female half-orc beautyqueen in training (The Lone City in the Wildlands) OSRIC
Halfpint - female halfling badgirl wannabe (Lab Lord- The North Marches) LL
Mark'd - charismatic human fighter (Lab Lord- The North Marches) LL


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AleBelly
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Re: Skill Check Probabilities

#3 Post by AleBelly »

Nice graph! I have a similar table that helps me decide which level of skill check to use.
Zhym wrote: The professors in my Ph.D. program would give me grief for using a line chart to represent discrete probabilities, and I feel a little unclean for doing so, but it's a lot easier to read than a clustered bar chart.
<rant>It drives me nuts when academics get dogmatic about this sort of thing. The purpose of graphs is to communicate data/information in a digestible format. With five separate conditions, this graph is the best way to clearly show that information...the lines "guide the eye."</rant>

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Norjax
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Re: Skill Check Probabilities

#4 Post by Norjax »

Nice graph. 8-)

Does anyone know if the Unseen Servant Dice Roller, for example, determines 4d6 as a random number from 4-24 or does it roll (4) 1d6 and then add them together?

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AleBelly
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Re: Skill Check Probabilities

#5 Post by AleBelly »

Based on the output from those types of rolls, I'm virtually certain it does the latter (which is what it should do...)

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ToniXX
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Re: Skill Check Probabilities

#6 Post by ToniXX »

Norjax wrote:Does anyone know if the Unseen Servant Dice Roller, for example, determines 4d6 as a random number from 4-24 or does it roll (4) 1d6 and then add them together?
AleBelly wrote:Based on the output from those types of rolls, I'm virtually certain it does the latter (which is what it should do...)
It rolls individual dice then adds them together.

Good analysis of the skill check method, Zhym.
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Norjax
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Re: Skill Check Probabilities

#7 Post by Norjax »

AleBelly wrote:Based on the output from those types of rolls, I'm virtually certain it does the latter (which is what it should do...)
Correct, thanks. I wasn't sure if the above results were from the die roller.
ToniXX wrote:It rolls individual dice then adds them together.
Good. Thank you.

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