# Challenging--- Central Limit Theorem

• Apr 22nd 2008, 02:17 PM
GoDuke
Challenging--- 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 PM
mr fantastic
Quote:

Originally Posted by GoDuke
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?"

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?