What is the probability that a 45-year-old man with an FEV of 4.0 L will be functionally impaired by age 75? 

Pulmonary Disease

Forced expiratory volume (FEV) is an index of pulmonary function that measures the volume of air expelled after 1 second of constant effort. FEV is influenced by age, sex, and cigarette smoking. Assume that in 45- to 54-year-old nonsmoking men FEV is normally distributed with mean = 4.0 L and standard deviation = 0.5 L.

In comparably aged currently smoking men FEV is normally distributed, with mean = 3.5 L and standard deviation = 0.6 L.