Elementary statistics

Question

Use a normal approximation to find the probability of the indicated number of voters. In the case, assume that 183 eligible voters aged 18-24 are randomly selected. Suppose a previous study showed that among eligible voters aged 18-24,22% of them voted. Probability that exactly 45 votes

Answer 1

If you're using the normal approximation, you're going to use n, p, and q from your binomial distribution to calculate a mean and standard deviation that you can use with a z-score. That is what 'normal approximation' means.

So, in your case:

n = 183

p = 0.22 (because 22% voted)

q = 1-0.22 = 0.78 (the % who didn't vote)

mean = n*p = 183*0.22 = 40.26

standard deviation = sqrt(n*p*q) = sqrt(183*0.22*0.78) = 31.4028

Now, you're ready to plug that into a z-score formula. :) Do you know what to do next?