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Math Help - Maths problems - Probablity and Statistics....Never go in my head

  1. #1
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    Maths problems - Probablity and Statistics....Never go in my head

    Dear All Probablity and Statistics GURUS

    I need this help, i have a question for assignment and I really dont kknow how to do that. It might be damn simple, but for me its like breaking the DNA code.

    Q1. Find the probablity that 3 heads in 5flips of a balanced coin?
    Q2.Find the probablity that LESS THAN 4 heads in 5 flips of a balance coins?

    Q3. Find the probablity that MORE THAN 3 heads in 5 flips of a balance coin?

    Q4. A production process produces 10 defective items per hour. Find the probablity that 4 or less items are defetive out of the output of randomly chosen hour using
    a) The Poisson Distribution and
    b) The normal approximation of poisson.


    Please help me folks. Really appreciate it.

    Thanks in Advance
    Masood
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by masood View Post

    Q1. Find the probablity that 3 heads in 5flips of a balanced coin?
    Q2.Find the probablity that LESS THAN 4 heads in 5 flips of a balance coins?

    Q3. Find the probablity that MORE THAN 3 heads in 5 flips of a balance coin?
    The probability of n heads in 5 flips has a binomial distribution B(5,0.5), so:

    p(n\ heads)=b(n;5,0.5)={5 \choose n} 0.5^n (1-0.5)^{5-n}

    Q1: just use the formula above with n=3

    Q2: let n denote the number of heads, then p(n \le 4)=1-p(n=5)

    Q3: let n denote the number of heads, then p(n > 3)=p(4)+p(n=5)

    CB
    Last edited by CaptainBlack; July 10th 2009 at 08:57 AM. Reason: sort out notational convention
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