I've been crafting stuff since professions came out and I've always wondered about rates for potential and stuff like that. Then last weekend I decided to finally do a little experiment. Below is the link for 1000 sharp green leather belts. Since statistics is not my best subject I'll leave you guys to do the hardcore stuff.
Edit: I forgot to include details XD. This was done on mules with level 1 crafting. I don't know if that's relevant to chance for potential or not. Also I noticed that every time I got a "Cool" when crafting the belt came out with potential. Whenever I got "Good" it was without potential. "So so" was the one that confused me because I've had it come with and without potential.