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Yeah, there have been various iterations of these probabilities posted in different combinations. Stalker0 did a bunch of them right after 4e came out and then there have been a few updates.
You are using the errataed SCs? Some of the higher complexity numbers look a bit low when you go with the SC errata where all complexities have 3 failures.
When characters have different chances of success on skill challenges, these probabilities become more complex. On the WotC boards, Elder Basilisk used an approximation based on the geometric average of each party member's chance to succeed on a roll (Skill challenges).
I'm pretty convinced that this systematically underestimates the chance to succeed on the skill challenge as a whole (my reasons here), while using the arithmetic mean would lead to results that could be above or below the true probability. That said, his basic points hold up fine:
Characters with weak skills should never try to roll them on a skill challenge; the best strategy is to declare you're using your best skill, giving some possibly ridiculous explanation why it's relevant, or else to avoid participating at all for fear of being called on to use a weak skill (since participating is typically optional). Characters should also use Aid Another as much as possible, which combined with the other suggestions could make skill challenges trivial. A naive strategy of "rolling for it" without using "Aid Another" works on easy challenges, but is unlikely to work on tough ones.
A sophisticated programmer could probably find a good way to "brute force" these calculations; simply running 100,000 simulations for each set of values is also a valid approach.
Well, you can do it for a given skill challenge fairly easily. Its just a simple sum of probabilities really. If everyone has to participate and discounting Aid Another its not hard at all. Aid Another is also not really ever mentioned as an option in SCs except for "group checks". So personally I maintain AA doesn't apply to normal SC rolls and nothing WotC has ever published AFAIK is contrary to that. The very existence of secondary skills kind of indicates its not really supposed to be possible since AA would be equivalent to a DC10 secondary skill use and for most SCs that would be easier than any secondary (which often have difficult level DCs).
As for the option to "do nothing", its certainly not excluded by the core SC mechanics, but no DM should write an SC that allows that. Every character who is present and participating at all should have to make some kind of die roll. Otherwise you might as well just have the guy with the super high skill bonus in one primary skill sit there are roll a bunch of dice.
The trick is to be able to calculate any kind of odds with various possible secondary skills, failure canceling rolls, one-time skill uses, etc. It can be done, but much like the issue with modeling combat you just never know what people will actually decide to do. Assuming they max their probability of success is logical but it would be nice to be able to compare options and see what happens when you change your SC design a bit.
At the risk of sounding like a broken record, I would like to reiterate that I think the "three failures" model and the "failed skill check results in a failure" condition is a very poor setup for skill challenges in general.
At the risk of sounding like a broken record, I would like to reiterate that I think the "three failures" model and the "failed skill check results in a failure" condition is a very poor setup for skill challenges in general.
Well, I ran a number of SCs using Obsidian SC system and what I've found is between it and the updated 4e system there are SOME differences, but not as much as you might think. Obsidian eschews failures, but in essence they still exist in that anything that isn't a success is a failure. In fact it deters people from using secondary skills in that they either have to also contribute to the success count or else they are effectively failures. It does pretty much mandate that everyone participate (I guess you could sit on your hands, but it would just hurt the party). So it has a couple of strengths, but equally the more structured round based mechanics can be too constraining at times.
In any case, if someone has come up with some other set of mechanics that doesn't involve counting up how many times you made your DCs I for one want to hear about it. I can easily structure a ADVENTURE that way, but any kind of activity can be broken down to SCs. If it involves a branching plot line then it should be multiple SCs and that's about the only other way I can think of to structure that kind of activity is as some sort of "flow chart". It would simply be a slightly different way of deciding what die roll counts for what in the end.
In my next game, I'm running a mystery type plot. Lots of roleplaying to investigate the source of the mystery, with an ambush in the middle and a boss fight at the end. The RP will be a skill challenge, with the results of the challenge determining how prepared they are for the boss fight: full success will have them surprise the boss and rescue his captives, partial success will have the boss ready for him, and he'll execute the prisoners when the party attacks, and a failure will have the party not even find the bosses lair, so he'll attack them elsewhere, and as a result, they won't get his treasure.
We've been using Obsidian, but the one thing I don't like about it is the strict 3 round structure -- it can get in the way of an RP scene, especially a long open-ended one like I plan for this scenario. So I'm going to try something new for this adventure: I'm giving each player 3 tokens, representing their three tries in the skill challenge. I'll call for skill checks left and right during the RP as they investigate the mystery, but it's up to the players to decide when to use a token -- the actions they use tokens on will have more significant results, pass or fail. For example, a player might decide to use one of his tokens on a Streetwise check while trolling for info at a bar. A success without the token might only get him one item from my list of secrets, while with the token he'll get three. A failed check without a token might not get any ill effect, but with the token, a failure might attract the bad guys attention and provoke the planned ambush attack. PCs won't be allowed to use a token for a skill they've already succeeded with in the SC, but of course they can still make the check without a token.
So the players will still be making 3 checks each in the skill challenge, but they won't be forced to act in turn, or forced to stop acting just because they've already done something this round, even if there's something to do that their PC is best suited for (like, say, the Bard not being able to sweet-talk someone because he's already acted).
The errata changes the complexities. That will totally change your results.
You're right, I'm going to edit the first page and make it clear how many successes and failures I've calculated those results with.
Quote:
Originally Posted by keterys
It's 2 + 2*C, not 3*C successes needed. But the errata is what made it 3 failures max, so you at least had that already.
Ok, so the results above should still apply for Complexity 2 Skill Challenges.
They need 6 successes before 3 failures in both systems.
Quote:
Originally Posted by AbdulAlhazred
In any case, if someone has come up with some other set of mechanics that doesn't involve counting up how many times you made your DCs I for one want to hear about it.
Slightly off-topic, but I recommend you this articles:
A sophisticated programmer could probably find a good way to "brute force" these calculations; simply running 100,000 simulations for each set of values is also a valid approach.
The above calculations are exact.
The calculus is somewhat complex, because it first makes a tree of all the possible paths of rolls:
For each path it determines if it is a success or a failure (just by looking at the last roll), it calculates it probability and finally it adds all probabilities for successes, and for failures.
You can even tell the algorithm to run the calculus with different chances for each roll.
What this does is to generate "solution paths", that is, a series of successful rolls or failed rolls in several combinations.
(a path is solved if it has enough successful rolls or enough failed rolls)
It collects all solution paths.
It will then ask it's "successChance" and it will sweep all successfull outcomes and sum up their individual probabilities.
How an incomplete solution path, gives it's next two solution paths, and some other helper methods:
One thing it doesn't take into account though is that rarely party members are using skills with exactly the same bonus.
For example, Fighters tend to have weaker skills in general. There best skills (like athletics or endurance) are often hindered by ACP, which lowers the max value.
Also in my experience certain skills are more coveted and certain classes more willing to take magic items and feats to bump skills.
A rarely see a player take skill focus streetwise, but skill focus perception...sure.
Now you can average the party's bonus and run the numbers that way but its not completely accurate (an average value provides higher success rates in general then looking at extreme values).
I think you can do the calculations more easily by simply summing the probabilities of failures. It actually doesn't matter what the sequence of rolls is. So for complexity 1 its 7 rolls with less than 3 failures. So all you need to know is the chance in 7 rolls of 3 dice coming up below N. That number is 7/(21-N)*.05 + 6/(21-N)*.05 + 5/(21-N)*.05 is it not?
One thing it doesn't take into account though is that rarely party members are using skills with exactly the same bonus.
Mmm, I don't know what you mean here.
This calculation takes into account the success chance of a roll.
It doesn't account for skill bonuses or DCs.
You mean that it is rare that a party has always the same chance for each roll accross a SC?
Quote:
Originally Posted by Stalker0
Now you can average the party's bonus and run the numbers that way but its not completely accurate (an average value provides higher success rates in general then looking at extreme values).
I ran some cases, which I don't consider conclusive in any way.
Here are the results:
Success chance for Skill Challenges complexity 2 (Need 6 successes before 3 failures)
I think you can do the calculations more easily by simply summing the probabilities of failures. It actually doesn't matter what the sequence of rolls is. So for complexity 1 its 7 rolls with less than 3 failures. So all you need to know is the chance in 7 rolls of 3 dice coming up below N. That number is 7/(21-N)*.05 + 6/(21-N)*.05 + 5/(21-N)*.05 is it not?
Mmm, I'm not sure about that.
In any case, I chose not to go that way because I wanted to analyze the case where you had different chances for each roll of the SC.
And you can't do that with a formula (at least not in this case).
That's why I needed a program like the one I did, so you can feed it an arbitrary sequence of chances and calculate the chance of succeeding in the skill challenge.
Last edited by sfedi; 7th November 2009 at 03:50 PM..
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