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Thread: Calculating Probability

  1. #1
    Join Date
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    Default Calculating Probability

    Any of you brainiacs care to explain how to calculate odds of hitting with dice? Every time I think I understand it, I get confused about it again.

  2. #2
    Join Date
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    http://www.unseelie.org/cgi-bin/dice...s+once+to+send
    and your statistics course will help you :P

    Generally it's not super difficult

    you hit on 3+ -> your six sided dice have 1/6 (rolling a 1) + 1/6 (rolling a 2) are misses and 4x 1/6 (rolling 3-6) are hits. This means base chance of a single dice is 2/6 (or 1/3) miss, 4/6 (or 2/3) hit -> 66.6%

    now if you have 2 dice you can have:
    miss+miss, hit+miss, miss+hit, hit+hit OR differently expessed 1x (2xmiss), 2x (miss+hit) (any order) and 1x (2xhit) -> which is then
    [A] 1x (2x 1/3) for double miss; [B] 2x (1/3+2/3) one hit any order; [C] 1x (2x 2/3) double hit. Now the chance to have at least one hit is [B]+[C] = 2x (1/3x 2/3) + 1x (2x2/3) = 8/9 => 88.88%

    With 3 dice it's the same, just another dice to add. Don't forget, since we do not worry about the order of the dice, you need to multiply the chances for each position a miss or a hit can happen. For example a one hit of 3 dice is
    2/3 (hit of the first dice) x 1/3 (miss of the second) x 1/3 (miss of the third) then the whole thing x3 -> as you can have a 1 of 3 if the first and third misses but the second hits and the first two misses but the third one hits.

    Hope this helps
    Last edited by jwalker; 07-16-2018 at 03:13 AM.

  3. #3
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    Ok so let me try this:

    The odds of getting at least 2 hits with 4 dice is:
    2/3^4 + 4(2/3^3x1/3) + 6(2/3^2x1/3^2)

    =.88888888...9

    Correct?
    (Exactly the same odds as getting 1 or more hits with 2 dice)

    ...no. It should be:
    (H)^4 + (HHHM)^4 + (HHMM)^6

    Exponential is not the same as x4 or x6
    Last edited by Ithamar Conkey; 07-22-2018 at 12:07 AM.

  4. #4
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    correct or easier
    chances of at least 2 hits = 100% - chance of getting only one hit or less

    -> 1 - 4*(2/3*1/3) -(1/3*1/3)=0.89

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