Question

Using the binomial distribution formula below, calculate the following: An online social networking website defines successes if a Web surfer stays and views its website for more than three minutes. Suppose the probability that the surfer does stay for more than three minutes if 0.16. What is the probability that at least four (either four or five) of the next five surfers will stay for more than three minutes?

b(x; n, P) = { n! / [ x! (n - x)! ] } * P^x * (1 - P)^{n - x}

Answer 1

Let X be the number of surfers out of next 5 surfers staying more than 3 minutes .

Then X~ Bin ( 5 , 0.16)

   , x = 0,1,2,3,4,5

P[X = 1] = (*) (0.16)*(0.84) --

To find P[ X= at least 4] = P[X = 4] + P[X= 5]

   

= () (0.16*(0.84)*- + ((0.165(0.89) = 0.0029