Chapter 14.5, Problem 30E

Refer to Exercise 14.29. Estimate the difference in the fractions of adult permanent residents with lung disease for cities A and B. Use a 95% confidence interval.

14.29    A survey was conducted to study the relationship between lung disease and air pollution. Four areas were chosen for the survey, two cities frequently plagued with smog and two nonurban areas in states that possessed low air-pollution counts. Only adult permanent residents of the area were included in the study. Random samples of 400 adult permanent residents from each area gave the results listed in the accompanying table.

1. a Do the data provide sufficient evidence to indicate a difference in the proportions with lung disease for the four locations?
2. b Should cigarette smokers have been excluded from the samples? How would this affect inferences drawn from the data?