D&D 4E Showing the Math: Proving that 4e’s Skill Challenge system is broken (math heavy)

silentounce

First Post
nittanytbone said:
Additionally, I think the designers deliberately low-balled things and made the skill challenge system HARD under normal circumstances. This allows the DM to hand out +2 bonuses for good ideas like candy and accounts for the players picking up magic items with significant skill bonuses without anything breaking.

This may be true, but if it is, they need to tell us that. It's not good enough to expect someone to crunch the numbers ahead of time and figure it out. Or realize it after a dozen skill challenges that the PCs never seem to be able to win.

I'm going with they didn't know.
 

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Spatula

Explorer
FadedC said:
Where are you getting the extra +5 to the DC from? Reading the DMG it just says to use the difficulty by level table, and that's only 15 at level 1 for a medium challenge. I'm assuming I must be missing something but I can't see anything about a +5.
It's the footnote to the DC table on page 42. I didn't notice it at first, either.
 
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Spatula

Explorer
Ydars said:
Stalker; your math doesn't seem to include the fact that some players can roll a skill that does not contribute to successes or failures (called a secondary skill in the DMG) but does give other party members +2 to other related skill rolls (see DMG)
Secondary skills in a challenge are the "imaginative" uses of skills that are not a normal part of the challenge (using Religion to escape guards chasing you, frex). And those checks are automatically at the hardest DC (25 at level 1, using the DMG charts). While a few official challenges have included "does not count as success but gives a +2 bonus to next roll" checks, I don't see any mention of that mechanic in the section on building skill challenges.

You may be thinking of "group skill checks" where one person makes the roll and everyone else aids another, but the DMG implies this is only for certain situations. I don't think this should be a common or even desired tactic for beating all skill challenges, because one of the stated goals of the challenges is to engage the entire group. Having 80% of the players make DC 10 checks while one player makes the "real" check does not accomplish that.

I think for now I will be ignoring the +5 DC for skill checks bit. At the very least it discourages characters without relevant skills from actively participating in the challenge - the DCs are so high that they are either reduced to aiding another or making a near-automatic failure.
 
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Spatula

Explorer
Cadfan said:
Does this math match up with anyone's play experiences? I have trouble believing that playtesters worked at this game for as long as they did without ever noticing that their party fails 80% of all skill challenges. Perhaps some factor is being omitted?
It's possible the playtesters reported their experiences and nothing was changed. They're all still under NDA so we have no way of knowing either way.
 
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Kaodi

Adventurer
Tervin said:
Being a maths teacher I trust my numbers ;)

Complexity 1: 0.256
Complexity 5: 0.147

(Both numbers approximate of course.)

Actually, when I started trying to do an easy challenge (w/ 0.8 and 0.2), I saw that my numbers were screwed up and I went back to look at my math. I had been doing 5C4 x (0.55)^4 x (0.45) + 4C4 x (0.55)^4 for Complexity 1, but after I reviewed the last time I did probability, I realized it should have been 4C3 x (.55)^4 x (0.45) + 3C3 x (0.55)^4, and got the same numbers you just did (once I had it right).

Anyway, one other factor that should probably be considered in determining what probability of success is right for a Complexity 5 challenge is how bad the negative consequences are. If failure means death, then it should probably be as difficult as the equivalent combat encounter. The less harsh the consequences are, the harder it should be.
 

keterys

First Post
Spatula said:
It's the footnote to the DC table on page 42. I didn't notice it at first, either.

And if you don't include that footnote, the math actually works out to a respectable chance of success for PCs... hence my theory that it's a mistake somehow :)
 

Kaodi

Adventurer
The problem is that if you look at the DC for a 1st Level Trap, which awards the same experience as a Complexity 1 Challenge, the DC to disable it is 25.
 

Simon Marks

First Post
keterys said:
And if you don't include that footnote, the math actually works out to a respectable chance of success for PCs... hence my theory that it's a mistake somehow :)

It's not, check the H1 web extra (the Skill Challenge) which shows a Level 6 Skill Challenge - which has moderate DC checks of 22. 17 is the moderate check for a skill at level 6, so +5 = 22.

Obviously, a 6th level wizard trying to deal with a DC 22 Arcana check will have d20 + 3 (level) + 5 (Trained) + 4 (Attribute) or d20 + 12. This could be as high as d20 + 17 with an Eladrin with a Skill focus.
 


Spatula

Explorer
Kaodi said:
Anyway, one other factor that should probably be considered in determining what probability of success is right for a Complexity 5 challenge is how bad the negative consequences are. If failure means death, then it should probably be as difficult as the equivalent combat encounter. The less harsh the consequences are, the harder it should be.
Well, there's a place for encounters that the group only has a 25% chance to complete successfully. But the skill challenge is supposed to be like a non-combat version of a combat encounter, and most combat encounters are designed with the assumption that the PCs will win. Reading the section in the DMG certainly doesn't leave one with the impression that the players should be failing the majority of challenges - they are presented as a way to make skill-based encounters that have a risk of failure, which makes the encounter more interesting. There's a risk that players might be defeated in an equal-level combat encounter, too, but that's not the norm, nor should it be.
 
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FadedC

First Post
Spatula said:
It's the footnote to the DC table on page 42. I didn't notice it at first, either.

Ah there it is. Ok so it seems like the general rule is that a trained character with an 18 stat should succeed at easy 75% of the time, medium 50% and hard 25%. This seems completely reasonable until you have skill challenges that require twice as many successes as failures.

A simple band aid fix would be to simply change the complexity rules. Require 4 successes before 4 failures and you should see average skill people completing their tasks half the time while those with extra skill bonuses will have a chance to shine.
 

CSK

First Post
The percent chance to get 2K successes before K failures with probability of success P is:

Code:
 \K  1    2    3    4    5
P \-------------------------
.05  0.2  0.0  0.0  0.0  0.0
.10  1.0  0.0  0.0  0.0  0.0
.15  2.2  0.2  0.0  0.0  0.0
.20  4.0  0.7  0.1  0.0  0.0
.25  6.2  1.6  0.4  0.1  0.0
.30  9.0  3.1  1.1  0.4  0.2
.35 12.2  5.4  2.5  1.2  0.6
.40 16.0  8.7  5.0  2.9  1.8
.45 20.2 13.1  8.8  6.1  4.3
.50 25.0 18.8 14.5 11.3  9.0
.55 30.2 25.6 22.0 19.1 16.7
.60 36.0 33.7 31.5 29.6 27.9
.65 42.2 42.8 42.8 42.6 42.3
.70 49.0 52.8 55.2 57.0 58.4
.75 56.2 63.3 67.9 71.3 74.2
.80 64.0 73.7 79.7 83.9 87.0
.85 72.2 83.5 89.5 93.1 95.3
.90 81.0 91.9 96.2 98.1 99.1
.95 90.2 97.7 99.4 99.8 100.

Of course this doesn't clarify how DCs should be assigned, but these are the probabilities we need to compare things.
 

MyrddinE

First Post
Consequences for Failure

The way I see it, the consequences for failure at the typical skill check is notably lower than that for failure in combat; thus, failure can be more common.

Using the chart above, and the theory that some checks in a skill encounter will be easy (aided by others, smart idea, etc) while others difficult (nobody has a relevant trained skill), I'd say that my group will likely be succeeding around 2/5 of the time on simple challenges, and 1/4 on complex challenges.

If the consequences for failure are drastic... such as death... then the challenge should be easy. It's as simple as that. Combat challenges are EASY for equal level fights, and moderate for hard boss-level fights... combat fights are NEVER difficult unless you go beyond the recommended level ranges. Skill challenges are harder by default because they are hinderances rather than life or death struggles most of the time.

You want some information about the baron? Maybe you can research history in the local archive... it's a difficult challenge to do, but if it fails you can try other challenges; you aren't going to die, but you might be tossed into a fight (an easy challenge).
 

Inf Class

First Post
I'm sorry if this has been pointed out already:

The footnote you mention (the +5) is for skill CHECKS, not skill CHALLENGES. The DMG notes that checks and challenges are very different. My interpretation will be that +5 is only for singular checks. I don't feel like doing the math, but this should increase the chances of success by at least 20%, shouldn't it?
 

Spatula

Explorer
Welcome to EN World!

Inf Class said:
I'm sorry if this has been pointed out already:

The footnote you mention (the +5) is for skill CHECKS, not skill CHALLENGES. The DMG notes that checks and challenges are very different. My interpretation will be that +5 is only for singular checks. I don't feel like doing the math, but this should increase the chances of success by at least 20%, shouldn't it?
But a skill challenge is made up of skill checks. :) As mentioned, the web extra skill challenge for KotS uses the lvl 4-6 DCs with the +5 added in. The one challenge present in the published KotS uses DC 15, which would seem to imply not using the +5, but it also involves 4 successes before 4 failures (instead of 2), so it's not a standard skill challenge (or a beta version, at least).

Perhaps the designers are just as confused as we are. :)
 

Terramotus

First Post
Cadfan said:
Does this math match up with anyone's play experiences? I have trouble believing that playtesters worked at this game for as long as they did without ever noticing that their party fails 80% of all skill challenges. Perhaps some factor is being omitted?
We ran two different skill challenges tonight. Both were straight out of the book. We, as the players, quickly realized that we had virtually no chance of successfully completing the Complexity 5 Urban Chase out of the book. The only option we saw was to have everyone do Perception (which doesn't cause you to succeed or fail, only provide a +2 or a -2 on the next roll) over and over until it was the turn of the guy with a +10 to Athletics and the guy before him got lucky with perception.

We decided that was utterly ridiculous. The DM ended up deciding to remove the +5 for skills, which, of course, made things much easier, perhaps a bit too easy.

It was the same thing in the second challenge too. We had to remove the +5. We're currently looking for a sane solution. As written, though, they're utterly broken, especially since you can't assume that every PC will have a good skill for the situation.
 

FireLance

Legend
The math behind skill challenges bothered me too. Then, I looked at the higher-level DCs and noticed something interesting (numbers from pg 42 of the DMG):

For levels 1-3, a moderate check was DC 15 (DC 20 for a moderate skill check).

For levels 28-30, a moderate check was DC 29 (DC 34 for a moderate skill check)

A 30th level character would have a +15 for level, say a +6 from ability scores, a +5 for skill training, and an unknown amount from magic (I haven't digested all the powers and magic items yet), for a total of +26. A trained character would thus succeed 65% or more of the time on an individual skill check, making it more likely that he can overcome a skill challenge without assistance.

So, the skill challenge system for 4e seems to require characters to work together (using Aid Another) to have a decent chance of overcoming the skill challenges at low levels, while allowing them to function more independently at higher levels.

So, what do you think: bug or feature?
 

Terramotus

First Post
FireLance said:
The math behind skill challenges bothered me too. Then, I looked at the higher-level DCs and noticed something interesting (numbers from pg 42 of the DMG):

For levels 1-3, a moderate check was DC 15 (DC 20 for a moderate skill check).

For levels 28-30, a moderate check was DC 29 (DC 34 for a moderate skill check)

A 30th level character would have a +15 for level, say a +6 from ability scores, a +5 for skill training, and an unknown amount from magic (I haven't digested all the powers and magic items yet), for a total of +26. A trained character would thus succeed 65% or more of the time on an individual skill check, making it more likely that he can overcome a skill challenge without assistance.

So, the skill challenge system for 4e seems to require characters to work together (using Aid Another) to have a decent chance of overcoming the skill challenges at low levels, while allowing them to function more independently at higher levels.

So, what do you think: bug or feature?
Bug, because none of that is mentioned at all. In fact, The wording for skill challenges very strongly implies that you CAN'T aid another, unless there's a specific skill for that task (such as Perception, in some of them). It also seems to be a bit of an exploit of the existing system to tie everyone up in an endless loop of Perception checks until the guy with the best odds comes up. Not to mention boring as hell on the higher complexity skill challenges.

If there is something missing, or some sort of misprint with the +5 for skill checks, then someone from WotC needs to address this. As written, the system just doesn't work.
 

helium3

First Post
We ran a 10th level skill check today as part of the mini-adventure I'm running them through. I did not include the +5 to Skill Check DC's, as I hadn't seen the foot-note the rest of you are talking about. Even then, they barely succeeded and only after a bunch of them started to aid some of the other characters. Now that it's been pointed out, Aid Another doesn't really seem like an option so I'm inclined to think there's merit to the idea that the skill challenges don't work very well.
 

hong

WotC's bitch
Terramotus said:
Bug, because none of that is mentioned at all. In fact, The wording for skill challenges very strongly implies that you CAN'T aid another, unless there's a specific skill for that task (such as Perception, in some of them).

?
The "Group Skill Checks" section in the Skill Challenges chapter would seem to be specifically about aiding another.
 

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