Out of 400 people sampled, 68 had kids. Based on this, construct a 99% confidence interval for the true population proportion of people with kids.

Question

___ < p < ___

Answer 1

68/400 = .17 + and - 3(sd)/sqr400

p = .17

.17 -.15sd < p < 17 + .15sd where sd = the standard deviation

that's a close approximation using the empirical rule 68-95-99.7

although it's often given as 99 instead of the more accurate 99.7%

use a z table or calculator to get a more accurate z score

if you don't know the population standard deviation, use the t distribution, but with n =400, there's little significant difference between z and t scores.