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I "reinvented the wheel" about a month ago trying to create a permutational table for a set of house rules I'm working on. I don't use excel, so this has involved rather a lot of cutting and pasting. After I solved for the first row, I realized that either my base formulae were completely wrong, or I had made too many errors in the process of making it. It hit me there are probably a few intelligent folks around here - math or engineering students, stats majors, or just plain experienced gamers who have made this sort of thing before - so I thought I would post the question.

-> for anyone with my level of math, a permuational table is one that gives, for a certain number of events happening that can each have a certain number of results, the odds for each potential combination of results. (a poor explanation and I must apologize) As a simple example, an autocannon shot by a BS3 Guardsman has a 50% chance to hit and two shots, so its permutational table for number of hits would look like:

0: 25%
1: 50%
2: 25%

The tables for one and two "shots" (or penetrations or routs or whatever) are pretty simple to find for anyone who can recall their grade 8 math class. I'm running into trouble at the tables for three or more "shots". I thought I had a formula worked out for it based on a "pattern" I thought I saw looking at the variables through a line (one shot) square (two shots) and cube (three shots) with the "hit" length/area/volume corresponding to a series of exponents based off the numerator and the denominator of the odds - a pattern I assumed would be replicated for four and five "dimensional" models - but having run the number for just the two table, I see that I made enough cock-ups either in concept or execution (arithmetic/algebra) to thoroughly foul any use I might get from it, and will probably be deleting the files as gobbledegook.

Thanks in advance for replies.

I think what you are after is (sorry if it is hard to follow - especially using simple forum text)

pS = chance off success
pF = chance of fail (1-pS)
^ = power (pS^3 same as pS cubed)
! = factorial

chance of X successes and Y fails from Z rolls = pS^X * pf^Y * (Z!/(X!*Y!))

so for 1 hit out of 2 autocannon shots

.5^1 * .5^1 *(2!/(1!*1!)) =
.5 * .5 * 2 =
.5

2 hits out of 4

.5^2 * .5^2 * (4!/(2!*2!)) =
.25 * .25 * 6 =
.375

Do you use any other spreadsheet - open office (free) has various stats functions, for this example of 2 hits out of 4 use BINOMDIST(2;4;0.5;0)

Puree (I hope you don't mind being capitalized) you are a gentleman (lady?) and a scholar. Thank you.