Question

Calculating Confidence Intervals

1. The average distance driven to work for a random sample of 55 people living in Columbus Ohio is 17 miles with a standard deviation of 2.2 miles. The average distance driven to work for a random sample of 30 people living in Cincinnati Ohio is 15.5 miles with a standard deviation of 1.7 miles. We are interested in a 95% confidence interval for the difference in average distance driven to work.

2. A study of teenage heroin use included a random sample of 112 boys and 133 girls between ages of 12 and 16 years selected randomly from public schools in Kentucky. Knowledge of heroin use by a family member was reported by 15 of the boys and 19 of the girls. We are interested in a 99% confidence interval for the difference in proportion of knowledge of heroin use by a family member between boys and girls ages 12 to 16 in Kentucky.

Answer 1

Solution:-

1) 95% confidence interval for the difference in average distance driven to work is C.I = (0.646 , 2.354).

C.I = 1.50 + 1.989 × 0.42934

C.I = 1.50 + 0.85396

C.I = (0.646 , 2.354)