Question

Assume that when adults with smartphones are randomly​ selected, 42​% use them in meetings or classes. If 15 adult smartphone users are randomly​ selected, find the probability that fewer than 5 of them use their smartphones in meetings or classes.

Answer 1

Let , X be the number of adults smartphone users who use their smartphones in meeting or classes.

P = 42% = 0.42 ,   n = 15

X follows Binomial distribution with n = 15 and p = 0.42.

We have to find P( x < 5 )

P( x < 5 ) = P( x <= 4 )

Using Excel function ,     =BINOMDIST( x , n , p , 1 )

P( x <= 4 ) = BINOMDIST( 4 , 15 , 0.42 , 1 ) = 0.1739

Probability that fewer than 5 of them use their smartphones in meetings or classes is 0.1739