So let’s talk about the internals of Partial Successes. To keep it simple, we’ll assume that the Challenge Rating (CR) is equal to the Skill Rating (SR), and that any second Challenges are made with the same skill against the same CR. (An assumption that doesn’t usually hold true, but which simplifies the math no end.)
Against an equal CR, the math breaks down as follows:
|Result||% Chance (Exact Result)|
|0 SR, Partial Success||27%|
|1 SR, Success||18%|
|2 SR, Solid Success||9%|
|3 SR, Spectacular Success||1%|
What the table is saying is that, if you only rolled once, you have an 18% chance of getting a Success (or 1 SR). Roughly 1 time out of 5, you just succeed. And 1 out of 100 times, you Succeed so well, people are impressed.
Which makes sense. When attempting a challenging task, we often fail. Sometimes we do spectacularly well, sometimes middling, and sometimes we only succeed by doing more work than other people. This my not be an exact match for the real world, but it is true-to-life: it matches what we experience in day-to-day life.
(And yes, the mechanics should match what we experience in day-to-day life, or should allow players to vicariously experience things they have no direct experience of, like fighting a grim, to-the-death sword duel or gun battle. “True-to-life” is my design goal.)
But there’s more, and describing it is a little complicated. (The mechanics are simple, it’s just the description that’s complicated.) A Partial Success (0 SR) happens 27% of the time. Getting 0 SR means you have to attempt another Challenge (or just take a Failure).
On that second roll, you can Fail or get 1 SR or higher. (Because, if you roll another Partial Success, it counts as a Success.) So, when everything is taken into account, that 27% gets divided up and distributed among the other results. That looks like the following:
|Result||% Chance (w/ 2nd roll)|
|0 SR, Partial Success||0%|
|1 SR, Success||30%|
|2 SR, Solid Success||11%|
|3 SR, Spectacular Success||1.2%|
So your chance of just Failing, giving the above assumptions, is 57%. Success is a 30%, and so forth. (The numbers in the chart are rounded off, which is why they don’t equal 100%.)
To some people, the 57% figure may seem high. It really isn’t, in two ways. First, it’s lower than the comparable number under the 5-count system (which was 60%).
Second, making a Declaration (a short in-character description of what you’re attempting) gives a +1 to the roll, which makes that Failure rate 46%. (Yes, when SR = CR, a +1 is a huge difference.) Spending a point of Resolve with that Declaration makes an even bigger difference (36% Failure), and having an applicable Distinction is even more influential (18%).
I’ve calculated the odds from SR = CR-9 (SR 10, CR 19) to SR = CR+8 (SR 10, CR 2), including how Declarations, Resolve, and Distinctions all affect the odds. Looking at the statistics, the model seems to hold up well.
It gives results that are true-to-life, while also being quite gameable. And since the mechanics themselves are very simple, all these probabilities are transparent to the end user.
It seems solid. At least, solid enough to take to testing.