Question

(5.2.22) Assume that when adults with smartphones are randomly​ selected, 36​% use them in meetings or classes. If 25 adult smartphone users are randomly​ selected, find the probability that exactly 17 of them use their smartphones in meetings or classes.
The probability is? (round to four decimal)

Answer 1

The 17 users from 25 can be chosen in ${25 \choose 17}$ ways . Chance that 17 users from 25 use their smartphones in meetings or classes is $0.36^{17}*0.64^8$ . The final probability is

${25 \choose 17}*0.36^{17}*0.64^8=\frac {25!} {17!8!}*0.36^{17}*0.55^8=0.0003$ or 0.03%