According to a CNN report, 7% of the population do not have traditional phones and instead they rely on only cell phones. In a random sample of 750 telephone users, what is the probability that more than 8% are "cell phone only?"

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- Apr 22nd 2008, 02:17 PMGoDukeChallenging--- Central Limit Theorem
According to a CNN report, 7% of the population do not have traditional phones and instead they rely on only cell phones. In a random sample of 750 telephone users, what is the probability that more than 8% are "cell phone only?"

- Apr 22nd 2008, 07:12 PMmr fantastic
Let X be the random variable

*number of cell phone only users*.

X ~ Binomial(n = 750, p = 0.07)

Pr(X > 60) = .......

Nowadays technology spits the answer out: 0.1581, correct to four decimal places.

The normal approximation to the binomial distribution could once upon a time be used. You should try using it. Compare to the answer above. How different is it?