7. A survey organization wants to take a simple random sample in order to estimate the percentage of

people who have seen Downton Abbey. To keep the costs down, they want to take as small a sample

as possible. But their client will only tolerate chance errors of 1% or so in the estimate. Should they

use a sample of size 100, or 2500, or 10000? An auxiliary source of information suggests the population

percentage will be in the range 20% to 40%

7. A survey organization wants to take a simple random sample in order to estimate the percentage of

people who have seen Downton Abbey. To keep the costs down, they want to take as small a sample

as possible. But their client will only tolerate chance errors of 1% or so in the estimate. Should they

use a sample of size 100, or 2500, or 10000? An auxiliary source of information suggests the population

percentage will be in the range 20% to 40%.

8. In a certain city, there are 100,000 people age 18 to 24. A random sample of 500 of these people is

drawn, of whom 194 turn out to be currently enrolled in college. Estimate the percentage of all persons

age 18 to 24 in the city who are enrolled in college. Give a 95.5% confidence interval for your estimate.

10. The National Assessment of Educational Progress tests nationwide samples of 17-year olds in school.

In 1992, the students in a random sample of size 1000 averaged 307 on the math component of the

test; the standard deviation of the scores was about 30.

Estimate the nationwide average score on the math test.

What is the standard deviation of this

estimate?