Q9b

1. A college professor wanted to determine if there was a difference between his two History sections in the proportion of students receiving A's. His 9:00 class had 9 A's out of 60 students and his 12:00 class had 10 A's out of 50 students. At ? = , test the professor's claim that there is no difference in the proportion of students receiving A's in his two sections.

2. A Roper survey reported that 65 out of 500 women ages 18-29 said that they had the most say when purchasing a computer; a sample of 700 men ages 18-29 found that 133 men said that they had the most say when purchasing a computer. At ? = , a test will be used to determine if there is a difference between these proportions. What is the null hypothesis?

3. A recent survey reported that in a sample of 400 students who attend two-year colleges, 108 work at least 20 hours a week. In a sample of 200 students attending private universities, 24 students work at least 20 hours a week. What is the 95% confidence interval for the difference of the two proportions?

4. A recent survey reported that in a sample of 400 students who attend two-year colleges, 108 work at least 20 hours a week. In a sample of 200 students attending private universities, 24 students work at least 20 hours a week. At a 1% level of significance, a test will be used to help deternmine if the proportion of students who work at least 20 hours a week is higher for students attending two-year colleges. What is the critical value?

5. A pediatrician claims that the standard deviation in heights of 10-year-old girls is greater than the standard deviation of heights for 10-year-old boys. A sample of 10 girls had a standard deviation of 2.5 inches and a sample of 8 boys had a standard deviation of 1.5 inches. At α = , does the evidence support the pediatrician's claim?

6. At a 5% significance level, a researcher claims that the variation in the amount of money spent on business dinners is greater than the variation in the amount of money spent on lunches. The variance of 9 business dinners was $ and the variance of 12 business lunches was $. What is the test value?

7. At a .05 level of significance, the Department of Transportation claims that there is no difference between the variation of federal highway money distributed to the northeastern states and the variation of federal money distributed to the central states. The standard deviation for 11 northeastern states is and the standard deviation for 12 central states is . What is the test value?

8. The Department of Transportation claims that there is no difference between the variation of federal highway money distributed to the northeastern states and the variation of federal money distributed to the central states. The standard deviation for 11 northeastern states is and the standard deviation for 12 central states is . Using a 5% level, what is the critical value?

9. A psychiatrist believes that children under stress will have a higher variability in their achievement test scores than those who are not under stress. A sample of 10 children under stress showed a standard deviation of 19 points on their achievement scores and a sample of 7 children not under stress had a standard deviation of 10.5 points on their achievement tests. At α = , is the psychiatrist's claim justified?

10. The afternoon stats section seems to have a higher variation in quiz scores than the morning section.

A sample of the afternoon quiz scores is:

A sample of the morning quiz scores is:

At a 5% level of significance, does the evidence support the claim that the afternoon section quiz scores have a higher variation than the morning quiz scores?