Binomial distribution

davehedgehog

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Apr 8, 2010
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I'm not too sure what to do with this question. I've attempted the first part. I'm not too sure what it's asking for b)i) and no idea what to do for b)ii). Any help is appreciated!

A road is constructed so that the right-turn lane at an intersection has a capacity of 3 cars. Suppose that 30% of cars approaching the intersection want to turn right, and they do so independently.
a) If 15 cars approach the intersection, what is the probability that the right-turn lane will not hold all the cars wanting to turn right?


Binomial(15, 3/10)

P(X>3) = 1 - P(X<3)
=1-.2969
=.7031

b) Over a week, 1428 cars used the intersection.
i) What is the distribution of the sample proportion of cars turning right at this intersection, in random samples of this size?

Is it just asking for: B(1428, 3/10)? Or am I supposed to do a calculation?

ii) What is probability that, in such a sample, the proportion turning right is between 0.28 and 0.32?
 
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