Do you get what you’re after?
My die of choice is of the twenty-sided variety, so success requires something more than the average. “Just passing” is in the double-digits, with true success being in the mid-to-upper levels of that. I showed you the d6 chart, here’s my d20 chart:
19-20 – Yes And (10%)
15-18 – Just Yes (20%)
10-14 – Yes But (25%)
05-09 – No But (25%)
02-04 – Just No (15%)
00-01 – No And (5%)
Why are there more “yeses” than “nos?”
This is initially based on my experience with improvisational theater — never say no. Saying no isn’t really so horrible — it’s just that when you do, the onus is on you to come up with alternatives. That can be a real pain on stage.
Too many “nos” and you don’t have a scene — you have an argument. This is intended to make things less taxing on your imagination — you want to tell a story, not fuss with straws. Also, while I’m technically talking about a whole bunch of things at the same time, the focus here is on the Single-Player Roleplaying Game.
There’s other reasons too, these numbers were partly chosen for a certain amount of recognize-ability — you might not easily succeed on the roll of a five to fourteen, but you can certainly tell the milestones from one another:
5-9 means you did “five or better, but less than ten.”
10-14 means you did “double-digits but less than fifteen.”
The result of “one or less” takes some doing, but when you manage it, something goes catastrophically wrong. Maybe you think failure should be more probable — I’d have to disagree. I’ve seen lots of it, and when things start going bad they tend to keep going downhill easily enough without help.
If there’s a resemblance to the pass-fail difficulty classes of D&D, that’s a little bit coincidence and a little bit intentional. They’re already recognizable numbers, but they’ve been tweaked ever so slightly to be easier to spot and read, and to modify the probability in the players’ favor. D&D usually manages to get one of these right.
All told, you have a fifty-percent probability that things will take a little more effort than maybe you were expecting — and yet you are slightly more likely to succeed than fail. You have what you were after and then you have to decide what to do next.