In a certain region, 15% of people over the age of 50 didn’t graduate from high school. We would like to know if this percentage is the same among the 25-50 year age group. What is the minimum number of 25-50 year old people who must be surveyed in order to estimate the proportion of non-grads to within 6% of the true parameter with 99% confidence?

235 people

Step-by-step explanation:

Given:

P' = 15% = 0.15

1 - P' = 1 - 0.15 = 0.85

At 99% confidence leve, Z will be:

= 1 - 99%

= 1 - 0.99 = 0.01

Z0.005 = 2.576

For the minimum number of 25-50 year old people who must be surveyed in order to estimate the proportion of non-grads to within 6%, we have:

Margin of error, E = 6% = 0.06

sample size = n =

= 235.02 ≈ 235

A number of 235 people between 25-30 years should be surveyed .

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.