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Help: S2 Binomial Distribution Question on Beads watch

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    A bag contains a large number of beads of which 45% are yellow. A random sample of 20 beads is taken from the bag. Use the binomial distribution to find the probability that the sample contains

    a) fewer than 12 yellow beads
    b) exactly 12 yellow beads

    I am struggling because the data isn't on the tables.

    Help much appreciated.
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    X~B(20, 0.45)

    n=20, p=0.45 is in tables, isn't it?
    For part (b) could use the formula.
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    (Original post by vc94)
    X~B(20, 0.45)

    n=20, p=0.45 is in tables, isn't it?
    For part (b) could use the formula.
    If I use n=20, p=0.45
    P(X<12) = P(X<11)

    But 11 is not on tables.
    Am I missing something?
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    P(X<12) = P(X<=11) in tables.
    Are you using Edexcel binomial tables?
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    (Original post by vc94)
    P(X<12) = P(X<=11) in tables.
    Are you using Edexcel binomial tables?
    Yes sorry it is on tables. Got it now.

    And I used the formula for part (b) and got it.

    Thanks!!
 
 
 
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Updated: April 12, 2011
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