Question

Thirty-five percent of adult Americans are regular voters. A random sample of 250 adults in a medium-size college town were surveyed, and it was found that 110 were regular voters. Estimate the true proportion of regular voters with 90% confidence and comment on your results.

Answer 1

Hence the true proportion is (0.388, 0.492).

Explanation:

Given n=250,

`p= 110/250 =0.44`

`a=0.1, |Z(0.05)|=1.645` (check standard normal table)

So 90% CI is

`p ± Z*√[p*(1-p)/n]\\0.44 ± 1.645*sqrt(0.44*(1-0.44)/250)\\ ( 0.388, 0.492)`