by Macnair » Thu Nov 10, 2005 5:31 pm
Case A. If you have 400+ wisdom,* it doesn't much matter what recipe you do: you will have about equal chances for skillups on both success and failure. (For some tradeskills you equalize chance-of-skillup for success vs failure at lower wisdom than this; at wisdom 415 you have equal chance-of-skillup for success vs failure on every recipe in the game.) So do combines that are cheap, or easy to farm, or easy to buy, or don't take many subcombines, depending on your wallet and your patience.
Case B. If your wisdom is below 400, your odds of gaining a skillup on success will be quite a bit higher than your chances of skillup on failure. (The further below 400 you are, the greater the difference.) So you should pick recipes that you have a good chance of succeeding, in order to have the best chance of skillups. Once you have 200+ skill, you should succeed in making your product 95% of the time on most any recipe with a trivial within 20 points or so of your current skill: anything light blue, half the things that are dark blue.
After applying the advice for Case A or Case B, it becomes a question of the Random Number Generator deciding to give you a skillup. This is very very streaky and can easily get you to pull your hair out. A typical example from when I was mastering pottery a couple months ago: one week, 120ish combines, 1 skillup; same recipe, 10 days later, 120ish combines, 8 skillups.
The short version is: runs of 100+ without skillup are quite common, and well within the limits of randomness.
The long version, complete with full mathematical formulas, has been posted by tradeskill devs at EQTraders for a long time.
* I say 'wisdom' because we are shamans; it actually is the highest of (wisdom, intelligence, alt_stat). Alt_stat is strength if you are doing smithing, and dexterity if you are doing fletching.