Question

assume that when adults with smartphones are randomly selected, 49% use them in meetings or classes. if 9 adult smartphone users are randomly slected, find the probability that at least 5 of them use their smartphones in meetings or classes.

Answer 1

49% of adults use smartphones in meetings or classes     
p = 0.49     
n = 9 (sample size of adults selected)    
     
Let X be the number of adults using smartphones in meetings or classes     
X ~ Binomial distribution with n = 9 and p = 0.49     
     
To find P(At least 5 of the selected adults use their smartphones in meetings or classes)     
that is to find P(X ≥ 5)     
P(X ≥ 5) = 1- P(X < 5)     
                = 1 - P(X ≤ 4)     
We use the Excel function BINOM.DIST to find the probability     
P(X ≥ 5) = 1- BINOM.DIST(4, 9, 0.49, TRUE)     
                = 1 - 0.5246     
                = 0.4754     
P(At least 5 of the selected adults use their smartphones in meetings or classes) = 0.4754     
Answer :     
0.4754