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Binomial distribution help!

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    I struggle how to find a value once it can't be gained from using the table. hard to explain so ill have to use a question.

    The probability of producing a read flower is 0.6. A gardener plants 20 of these bulbs.

    Find the probability that the number of read flowers produces is at least 12.

    I know you have B(20, 0.6) then B(20,0.4)

    at least 12 = (x greater than equal to 12) but looking at the answer/ mark scheme they've used (x less than or equal to 8). How do you get this?
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    Hi mate, hard to explain this one on here but I'll give it a shot.

    You've sussed the hardest part of it:

    If X - B(20,0.6) then 'X - B(20,0.4)

    So we are looking for the Probability that X>=12. Just think about it. If X is going to be 12,13,14.....20. Then 'X has to be 8,7,6........0

    So the probability of X>=12 is equal to the probability of 'X<=8.

    Now we can use the table.


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Updated: May 25, 2012
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