Question

The negative effects of ambient air pollution on children's lung function has been well established, but less research is available about the impact of indoor air pollution. The authors of an article investigated the relationship between indoor air-pollution metrics and lung function growth among children ages 6-13 years living in four Chinese cities. For each subject in the study, the authors measured an important lung-capacity index known as FEV₁, the forced volume (in ml) of air that is exhaled in 1 second. Higher FEV₁ values are associated with greater lung capacity. Among the children in the study, 518 came from households that used coal for cooking or heating or both. Their FEV₁ mean was 1421 with a standard deviation of 321. (A complex statistical procedure was used to show that burning coal had a clear negative effect on mean FEV₁ levels.)

(a.) Calculate and interpret a 95% (two-sided) confidence interval for true average FEV₁ level in the population of all children from which the sample was selected. (Round your answers to one decimal place.)

(b.) Suppose the investigators had made a rough guess of 320 for the value of s before collecting data. What sample size would be necessary to obtain an interval width of 50 ml for a confidence level of 95%? (Round your answer up to the nearest whole number.)

Answer 1