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# Help: S2 Binomial Distribution Question on Beads watch

1. 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

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

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

n=20, p=0.45 is in tables, isn't it?
For part (b) could use the formula.
3. (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?
4. P(X<12) = P(X<=11) in tables.
Are you using Edexcel binomial tables?
5. (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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