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

[silentounce]

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.

 

[Spatula]

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.

 

[Spatula]

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.

 

[Spatula]

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.

 

[Kaodi]

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]

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]

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]

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.

 

[Fredrik Svanberg]

I would like to know what mathematically talented people think about the idea I posted here: http://www.enworld.org/showthread.php?t=229928

 

[Spatula]

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.