The Data Set FEV.DAT on the Companion Website contains pulmonary function measures on 654 children ages 3-19 seen in East Boston, MA as part of Childhood Respiratory Disease (CRD) Study. The dataset contains data on age, sex, height (inches), FEV=volume of air expelled in 1 second (liters), and smoking status.

## Part (a) 5 points

Fit an appropriate model for FEV and find a 95% CI for the average volume of air expelled in 1 second for a non smoking male child.

## Part (b) 5 points Does this average significantly change if the height of the child is higher than the average height of children? Explain. ## Part (c) 5 points

Suppose you fit a linear model for FEV against all covariates provided in the data set. Do you see a reason to doubt the assumption of (i) normality (ii) equal variance and (iii) linearity against the covariate Age? Explain.