How Many Tails?

Discussion in 'Probability and Statistics' started by nycmathguy, Jun 18, 2022.

  1. nycmathguy

    nycmathguy

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    IMG_20220617_193652.jpg
     
    nycmathguy, Jun 18, 2022
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  2. nycmathguy

    MathLover1

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    you cannot ask a question "how many tails will come up"

    that should be probability question, like "A coin is tossed 20 times. What is the probability there are 7 tails?"

    The probability of getting k tails (or heads as probability for either of them is equal i.e.
    1/2) out of n trials (tosses) is given by
    P(n,k)=nCk(1/2)^k(1/2)^(n−k) where nCk=n!/(k!(n-k)!)
    n=20, k=7

    P(20,7)=20!/(7!(20-7)!)(1/2)^7(1/2)^(20−7)

    P(20,7)=20!/(7!(13)!)(1/2)^7(1/2)^(13)
    P(20,7)=4845/65536=0.0739288330078125
     
    MathLover1, Jun 18, 2022
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  3. nycmathguy

    nycmathguy

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    This is a problem I found at mathisfun.com. This is not my creation.
     
    nycmathguy, Jun 18, 2022
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  4. nycmathguy

    MathLover1

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    it's better to use a book, people are posting such of incomplete questions all the time (even on algebra.com)
     
    MathLover1, Jun 18, 2022
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  5. nycmathguy

    nycmathguy

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    I'll remember to do so.
     
    nycmathguy, Jun 18, 2022
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