Math 227 Statistics

Question

(6) When 319 college students are randomly selected and surveyed, it is found that 120 own a car.

a. Find a 99% confidence interval for the true proportion of all college students who own a car. Explain.

Answer 1

Even though we must estimate our population parameters from a sample, the Z distribution confidence interval must be used as this is a proportion

The formula for the C.I. will be =. [ p − z _α/2 *√(p∗(1−p)/n) , p + z _α/2 *(p∗(1−p)/n) ]

p = .37618 n = 319 z _α/2 = 2.576

answer = [.3743 , .3781]