MAT 1272 Statistics, SP2014

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    Ezra Halleck

    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)].



    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


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


    Chana Max, RN

    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

    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.


    Ezra Halleck

    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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