MAT 1272 Statistics, SP2014

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  • #13729

    Ezra Halleck
    Participant

    If a bent coin with probability of a head .3 is tossed 5 times, find the probability of getting
    a) exactly 4 heads b) eactly 5 heads c) at most 3 heads [use results from parts a) and b)].

    #17831

    Oruada
    Participant

    A) Exactly 4 heads= 4-(0.30)^5=3.99757=4
    b) Exactly 5 heads= 5-(0.30)^5= 4.99757=5
    c) At most 3 heads= 4+5-3(0.3)^5=2.43

    #17840

    Thus, would it be safe to claim the formula for this particular problem is: condition – (probability)^turns?

    #17844

    Chana Max, RN
    Participant

    I got a different answer, using both the formula (n nCr x)(P^x)(1-P)^n-x and Table 2 for Binomial Distributions i got:
    a) (5 nCr 4)(.3^4) (1-.3)^1=0.028
    b) (5 nCr 5)(.3^5)(1-.3)^0=0.002
    c) 0.028+0.002=0.03
    1-0.03=0.97

    key:parenthesis means multiply and ^ means to the power of (exponent)

    Professor please clarify this question and let us know the correct answer as soon as possible.

    #17848

    Ezra Halleck
    Participant

    The last submission (cmax) is correct.
    Oruada, a clue that something is wrong is that probabilities always are between 0 and 1. Something close to 0 happens infrequently and something close to 1 is likely to happen.

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