Does this take foils into account? And double foils? (I got one once!) Also, I hear that the probability of getting a rare foil was less than that of a common. Was that true? I have pulled foil promos Legolas, Son of Thranduil and Theoden, Lord of the Mark before and want to know what the chances of doing so were.
No, I ignored the possibility of foils in my calculations. I've been told that any booster box (sets 1-12, excluding 9) was guaranteed to have at least 1 R, 1 U, and 1 C, but I never saw anything official stating that.
A few scenarios for foils:
1) All foils are equally likely (i.e. when you open a foil, it has equal chances of any card in the set). My experience does not support this (I've opened far more common foils than rare foils). It is difficult to tell from the singles market if this is true because value is determined more by demand than supply (
Aragorn CoG foil is a common, but because people want him far more than
tWoaL foil, he costs more, which is believable even if his supply is greater than
tWoaL).
2) The guarantee mentioned above is true, and C are otherwise more likely than U/R; U are more likely than R. This means that a box with 6 foils (per Decipher's 1 foil/6 packs statement on the packs) could have a 4:1 ratio C to R. That's much better than the 7:1 ratio for non-foils, and it would mean that rare foils are more common relative to common foils than rares are to commons.
3) The guarantee mentioned above is false, and foils are distributed with the same 7:3:1 C/U/R ratio as normal packs.
Of course, this might be completely wrong and Decipher did something else for the relative probabilities.
I know nothing about double foils outside of set 9. I have seen foils (incl. foreign foils) in the non-set 9 part of set 9 packs, but since my model for how they constructed set 9 packs was to take whatever they had sitting around and put it into the bin, I can't attempt statistical analysis on those packs.