Fig. 1— Probability of true restriction (defined as total lung capacity<lower limit of normal) in males and females, respectively, using % predicted (% pred) for forced vital capacity (FVC) or forced expiratory volume in six seconds (FEV6), in the nonobstructive and obstructive groups. Nonobstructive: –––––: FVC, male; ------: FEV6, male; – – –: FVC, female; — — —: FEV6, female. Obstructive: ········: FVC, male; -- -- --: FEV6, male; –– · –– ·: FVC, female; — ·· — ·· : FEV6, female.