Question

Most sample surveys use random digit dialing equipment to call residential telephone numbers at random. the telephone polling firm zogby international reports that the probability that a call reaches a live person is 0.15. calls are independent. (a) a polling firm places 7 calls. what is the probability that none of them reaches a person?

Answer 1

The probability is 0.3206.
 
Since the probability of reaching a live person is 0.15, the probability of not reaching someone is 1-0.15=0.85.  

The probabilities are independent, which means to find the probability of not reaching anyone on all calls we find (0.85)^7= 0.3206.