What is Perception?

[Tregonsee]

In looking at dumps and my character's stats, I see the characteristic Perception and it seems to be done in "1 in xx".

What does this mean?

Is a low second number good? How can I get it to go up or down?

Is this affected by equipment/class/race/level, and how much?

[Derakon]

It measures how good you are at noticing hidden doors and traps without actively searching for them. Thus, lower numbers are good since they mean that you get free searching actions more often. Items that give boosts to searching will improve it, and IIRC each class gets a natural boost to it each level as well.

[Tregonsee]

Is 1 in 10 twice as good as 1 in 20, or is there a different function like in speed (higher levels are not as good)?

[Derakon]

I would assume it's twice as good, but I never really worried about it because it's such a useless stat; secret doors are almost always obvious and you should regularly be using trap detection magic or items.