A poll is given, showing 20% are in favor of a new building project.If 7 people are chosen at random, what is the probability that exactly 6 of them favor the new building project?

Respuesta :

Recall the binomial probability

[tex]\begin{gathered} P(x)=\binom{n}{x}\cdot p^x\cdot(1-p)^{n-x} \\ \text{where} \\ n\text{ is the sample size} \\ p\text{ is the probability of success} \end{gathered}[/tex]

We have the following given

n = 7

p = 20% → 0.2

x = 6

Substitute these values and solve for the probability

[tex]\begin{gathered} P(x)=\binom{n}{x}\cdot p^x\cdot(1-p)^{n-x} \\ P(6)=\binom{7}{6}\cdot(0.2)^6\cdot(1-0.2)^{7-6} \\ P(6)=\binom{7}{6}\cdot(0.2)^6\cdot(0.8)^1 \\ P(6)=0.0003584 \end{gathered}[/tex]

Therefore, the probability is 0.0003584.