Use a normal approximation to find the probability of the indicated number of voters. In this case assume that 150 eligible voters aged 18-24 are randomly selected. Suppose a previous study showed that among eligible voters aged 18-24, 22% of them voted.
The probability that fewer than 39 of 150 eligible voters voted is

Respuesta :

The number of people who voted follows a binomial distribution with probability of having voted [tex]p=0.22[/tex] and [tex]n=150[/tex] subjects, which means the approximating normal distribution should have mean [tex]np=33[/tex] and standard deviation [tex]\sqrt{np(1-p)}\approx5.07[/tex].

With the continuity correction, you have

[tex]\mathbb P(X<39)\approx\mathbb P(X<38.5)=\mathbb P\left(\dfrac{X-33}{5.07}<\dfrac{38.5-33}{5.07}\right)=\mathbb P(Z<1.08)\approx0.86[/tex]