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Hey mates,

Maybe my search-fu is weak, but I didn't find a thread where the odds to get a desired Psychic Power on a Random D6 table was calculated.
I always assumed that for a ML3 psyker, the chance to get for instance Iron Arm was >60%. I quickly reasoned 3*1/6+ rerolls on doubles would make for a >60% chance.
I wanted to check this because I'm dense on maths, so I wrote out all options on 3D6. I think I was wrong in my initial assumptions.

On a ML3 Psyker I found this:

There are 216 possibilities to start with.
91 of these get you (at least) one Iron Arm result. (42%). Remember, multiple 1's are no better than one 1.
Of the failures to get Iron Arm, 125 in all, 65 possible outcomes grant a reroll because of a double (+5% or 65/216*1/6), 5 of those grant a double reroll because of a triple (+0,7% or 5/216*2/6).
The combined chance to get Iron Arm (or whatever) on a ML3 model comes out to be 47,7% or <50%...

On a ML2 Psyker this is as follows:

There are 36 possibilities to start with.
11/36 chances to get (at least) one Iron Arm result. (30,5%)
5 rerolls of doubles (+2% or 5/36*1/6)
The combined chance to get Iron Arm on a ML2 model thus is 32,5% chance.

Can anyone verify?

Thnx!

Cilithan

Maybe I'm missing something, but aren't you over thinking this? If you roll three D6 untill you get three different numbers, isn't it just the case you've got a straight 50% chance of one of these three being Iron Arm?

Likewise, for level two there should be a 1/3 chance of getting it? That's how I've always thought it worked, happy to be corrected if I've over simplified things!

Technically speaking yes, but not really since they are in sequential order and you don't roll for psychic powers all at the same time order does matter.

ML3:
First roll 16.7% getting the power 83.3% failing.
2 cases:
Opt to take Primaris power
Not to take Primaris power

2nd Roll:
Case 1: Opted to take Primaris Power
16.7% of getting the power, 83.3% failing totaling of 30.62% of getting specific power.

Case 2: Opted not to take Primaris power
20% of getting the power, 80% of failing, totaling of 33.4% getting the power.

3rd Roll
Case 1->Case 1: Can't take Primaris power again.

Case 1->Case 2: Opted not to take Primaris power
20% of getting the power, 80% of failing, totaling of 47.32%

Case 2->Case 1: Opted to take the Primaris Power
20% of getting the power, 80% of failing, totaling of 49.4% getting the power.

Case 2->Case 1: Opted not to take the Primaris power
25% of getting the power, 75% failing, totaling of 53.4% to get the power.

Never take Primaris:
5/6x4/5x3/4 = 50% chance to Not get it. Added up to 1 you have a 50% chance of generating it.
PP On first Dice:
5/6x5/6x4/6 = 55.56% to Not get it. Added up that's 44.46% of getting it.
PP on Second:
5/6x4/5x4/5 =53.33% to Not get it. Added up that's 44.47% chance of getting it.

Matutss: You don't multiply the success together mate. You find out the chance of not getting something then subtract it from 1.

No total chance is: Previous failure rate time current success rat plus previous success rate

I ran these calculations for Telepathy a while back. For a desired power the chance on the first roll is 1/6

The chance to fail is 5/6 and on that probability branch you have a 1/5 chance to succeed. Rinse and repeat this process.

With ML 3 the chance to get any one psychic power is...

1/6 + (5/6)*1/5 + (5/6*4/5)*1/4

The brackets indicate a conditional probability and I am assuming you never swap for the primaris. As it turns out, this is exactly 50%.

First throw we have 6 possible outcomes and 5 we don't want. The next dice we throw we have 5 total possible outcomes, 4 of which we don't want. Next one is 4 total possible outcomes, 3 of them we don't want.
In total we've had 5*4*3=60 total possible results we don't want.
In total we've had 6*5*4=120 total possible results.
60/120 = 50.

lets say you want to find out what's the chance of hitting with a snapshot on, say, 6 throws? 1-(5^6/6^6) = 66% chance. 5^6 total possible outcomes we don't want, 6^6 total outcomes.

check out the more than 2 dice section here: http://gwydir.demon.co.uk/jo/probability/calcdice.htm#more
It explains it better than I.

1+2+2+1

Or was it 1+2+1+1


Automatically Appended Next Post:
http://www.youtube.com/watch?v=O5ROhf5Soqs

hahaha. clue the movie.
watch the whole thing if you have netflix (:

You either get it or you won't, so it's 50%.