D&D General Group Skill Checks (Too Many Cooks)

[Xeviat]

Hi everybody,

I got curious and was unable to find statistics for group skill checks, so I made a table to help me understand the probabilities. I've never taken statistics, so I'm sure there was a mathematical way to do it, but I just put it together using AnyDice (brute force using the counting function). I've been thinking of ways to handle exploration, especially when everyone jumps in and wants to roll for the same thing, even if it wasn't what they were in the middle of (this has been a very common thing amongst my group of players). I was thinking of "minimizing" this behavior by functionally changing the Help action from advantage to making the check into a group check: for 2 characters working together on one task, it's functionally the same as advantage (except each rolls with their own skill bonus). My suspicion was this would drop the chances of success when 3 people jumped in to do the same thing, which I started calling the "Too Many Cooks" effect.

Group skill checks require at least 50% of the party to succeed. That means 1/2, 2/3, 2/4, 3/5, and 3/6 for common party sizes. Odd numbers of PCs look like they'll make the checks harder, but how do the probabilities work out? Here's what I found:

Party Size vs Roll Needed (or +0 vs DC ?)

Party Size​	5​	10​	15​	20​
1​	80.00%​	55.00%​	30.00%​	5.00%​
2​	96.00%​	79.75%​	51.00%​	9.75%​
3​	89.60%​	57.48%​	21.60%​	0.73%​
4​	97.28%​	75.85%​	34.83%​	1.40%​
5​	94.21%​	59.31%​	16.31%​	0.12%​
6​	98.30%​	74.47%​	25.57%​	0.22%​

Unless I've coded things incorrectly, it looks like my assumption was right. Moving from 4 to 5 players does drop the probabilities. Also, group skill checks become harder than individual checks once you have 3 or more PCs and the chances are below 50%. 2 is always better than 1, but things drop from there.

So, this looks like you'll want to stick with relatively easy DCs for group skill checks, as Ability/Skill bonuses can be as low as -1 throughout the whole game. But, this does support my desire to make this change, along with letting the players know that 2 is the best number to work on a single issue.

Does this reflect project work to you like it does to me?

 

[abirdcall]

Most of the time I save group checks for a major scene and there will usually be partial successes available.

Also, I resolve them in an order that I thinkakes narrative sense and that order can influence further checks.

For example, someone succeeds on insight and is then able to inform the PC(s) doing the influence action giving them advantage (or whatever)

 

[ezo]

Does this reflect project work to you like it does to me?

Yep. It is a binomial distribution so here was what I got for DC 10:

Each even-group size gets slightly worse over the smaller even-group.
Each odd-group size gets slightly better over the smaller odd-group.

 

[Lakesidefantasy]

So, when doing group checks it is advantageous to leave the odd man out?

 

[GMMichael]

There's a fundamental flaw in your group-task resolution when success is more affected by whether the group size is odd or even instead of whether the group is large or small.

"Everyone knows that scouting parties should have two or four members. Three is right out."

Focus on why the group is rolling, then worry about how many successes you need. Better yet, recognize that group tasks are probably less black and white than individual tasks, so "success" or "failure" shouldn't be the end results.

 

[Lakesidefantasy]

"Everyone knows that scouting parties should have two or four members. Three is right out."

A quirk of living and operating in a not real world.

And, hand grenades.

 

[toucanbuzz]

My solutions for group checks has reduced the # of folks who roll when they clearly have no other reason than they might get lucky with the dice:

Searching, Foraging, Knowledge, etc.

• I only count the highest success. Any other successes are just concurring or duplicating effort. If failures outnumber successes, the failures actually convince the group they're correct. Otherwise I rule failures give cumulative -2 to the success roll and might turn a success into failure by sowing doubt or confusion into the group.

With this in play, my gamers are less inclined to try to roll Knowledge if they have no proficiency or background at all as they might, through their character's ignorance of the subject material, muddle the conversation.

Everyone needs to succeed, e.g. Stealth

• Any failures trigger a chance for a negative outcome, such as the enemy making a Perception check. I'm not a believer that if 3/4 folks are stealthy, that Fred the Fighter's failure while wearing heavy plate armor and bells is ignored.

Lending a Hand, e.g. Lifting a gate, putting out a fire

• I'm okay if it makes sense to allow the Help action (an 8 Strength character shouldn't be able to contribute to an 18 Strength character trying to lift a portcullis), or I set a threshold like in prior editions (it takes 25 total STR to lift the gate, two medium creatures can try).