Question

It is reported that 30 percent of American households use a cell phone exclusively for their telephone service. In a sample of nine households, find the probability that:

(a) None use a cell phone as their exclusive service. (Round your answer to 4 decimal places.) Probability

(b) At least one uses the cell exclusively. (Round your answer to 4 decimal places.) Probability

(c) At least six use the cell phone. (Round your answer to 4 decimal places.) Probability

Answer 1

Let , X be the number of American households use a cell phone exclusively for their telephone service.

Here , X has binomial distribution with parameter n=9 and p=0.30

Therefore , the probability mass function of X is ,

; x=0,1,2,.............,n and q=1-p

=0;otherwise

By using binomial probability table ,

(a) P(X=0) = 0.0404

Therefore , the probability that none use a cell phone as their exclusive service is 0.0404

(b)

Therefore , the probability that at least one uses a cell phone as their exclusive service is 0.9596

(c)

Therefore , the probability that at least six uses a cell phone as their exclusive service is 0.0253