Hey so I just noticed, the skill values on the work schedule don't always properly reflect how good someone really is. I went digging in my outer's stats and sure enough, someone might have a lower mining skill but have higher mining yield (which is what I'm really interested in when picking my miner). Skill seems to raise speed first, and yield a distant second. Same with farming, crafting, butchering, etc..., and tools only seem to increase speed (except perhaps for the acupuncture needles).
Some traits might also mess with things further, for instance "Gifted Artist" seems to double the effect of "Artisanry", which itself gives a boost to the final quality of items. A "Meticulous" character on the other hand, had a boost to the initial quality range of crafted items, which is related to the "Crafting" skill. And I'm pretty sure that the "Craftsman" trait (not to confuse with the background story) also gives a substantial bonus.
This, on a tangent, made me curious about how each stat increased ability, and after some testing, most of them aren't straightforward, so here it is :
Mining 50% PER, 50% CON
Farming 70% PER, 30% CON
Construction 100% CON
Crafting 50% PER, 20% INT, 30% LUK
Social 100% CHA
Artisanry 40% PER, 60% INT
Cooking 60% PER, 40% CON
Medecine 60% PER, 40% INT
Battle 40% PER, 20% INT, 40% LUK
Qi sense 60% CON, 40% INT
As for Magic and Magic Crafting, it's 100% concentrated power of will... errr I mean they're only correlated to skill level, and cap at 50.
[Edit] Also stars (passionate/obsessed) increase the base skill level as if you had trained the skill, which is always a nice bonus on skills that you can't actually train, but won't help if you're at 20/20.