From the information available;
The population is 52% and the sample size is 7. The probability that exactly 4 of them use smartphones (if 7 adults are randomly selected) would be calculated by using the formula given;
[tex]\begin{gathered} p=52\text{ \%, OR 0.52} \\ n=7 \\ p(X=x) \\ We\text{ shall now apply;} \\ p(X=4)=\frac{n!}{x!(n-x)!}\times p^x\times(1-p)^{n-x} \end{gathered}[/tex]We shall insert the values as follows;
[tex]\begin{gathered} p(X=4)=\frac{7!}{4!(7-4)!}\times0.52^4\times(1-0.52)^{7-4} \\ =\frac{5040}{24(6)}\times0.07311616\times0.110592 \\ =35\times0.07311616\times0.110592 \\ =0.28301218 \end{gathered}[/tex]Rounded to four decimal places, this becomes;
[tex](\text{selecting exactly 4)}=0.2830[/tex]ANSWER:
The probability of selecting exactly 4 smartphone users is 0.2830
