it is reported that 16 percent of american households use a

it is reported that 16 percent of american households use a cell phone exclusively for their telephone service. in a sample of seven households, find the probability that at least two use the cell phone exclusiviely for telephone service

A) .2478 B).7522 C) .3115 D) .2248 E) .7752

Solution

Note that

P(at least 2) = 1 - P(0) - P(1)

Note that the probability of x successes out of n trials is          
          
P(n, x) = nCx p^x (1 - p)^(n - x)          
          
where          
          
n = number of trials =    7      
p = the probability of a success =    0.16      
x = the number of successes =    0      
          
Thus, the probability is          
          
P(0) =    0.295090347      

Similarly, P(1) =

P(1) = 0.393453795

Thus,

P(at least 2) = 0.3115 [OPTION C]