1. True or false: In Figure 3 (page 435), the confidence level is 90%, so 90% of the intervals must contain . Explain your answer.

2. True or false: The curve is symmetric about 0, just like the curve is. Therefore, we can use all our symmetry techniques with the curve, too.

3. Suppose we cut a margin of error in half. The sample size requirement then becomes __________ times larger.

4. Our estimate of is __________ precise using the curve instead of the curve.

5. is used to find the value of . Is a probability or a value of or a value of ?

6. What are the conditions for constructing a interval?

7. College Education Costs. A random sample of 225 colleges yielded a mean cost of college education of $30,500 per year. Assume that the population standard deviation is $5000.

8. Crash Test Data. The National Highway Traffic Safety Administration collects data on crash tests for new motor vehicles. They reported that the mean femur load (force applied to the femur) in a frontal crash for the passenger in a Chevrolet Equinox SUV was 1003 pounds. Assume the data are normally distributed, the population standard deviation was 300 pounds, and the sample size was 9.

9. Independence for Quebec? A poll conducted by the newspaper La Presse reported that 340 of 1000 randomly chosen Quebec adults surveyed would vote “Yes” in a referendum for independence from Canada.

10. Tax Returns. In Example 10 in Section 3.2, Ashley and Brandon worked at an accounting firm preparing tax returns. Their Chief Accountant kept careful track of the amount of time (in hours) for all the tax returns that they prepared in the last week of March, shown in the accompanying table. Assume both data sets are normally distributed.

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11. Quality of Education in America. The National Assessment of Educational Progress (NAEP) administers exams to a nationwide sampling of students to assess the quality of education in America.

Suppose NAEP wants to estimate the population proportion of American schoolchildren who would answer a given question correctly. Find a sample size that would give a margin of error of 0.03 with 90% confidence.