Table 2

Descriptive statistics for height standardised lung function for 30–35 year old workers, and the lower limits of normal, and % rejected for the predicted and selected reference equations

Lung function Mean SD Skewness Lower 95% CI Lower limit of normal; % rejected for the different equations
Black miners, n=4503, age=32.6 (SD 1.7), height=1.7: Predicted Louw ECCS
 FVC (l)4.210.510.143.373.34; 4.4%3.44; 6.6%3.68; 14.9%
 FEV1(l)3.600.46−0.032.842.81; 4.3%2.78; 3.8%3.07; 12.5%
 FEV1%85.66.11−0.7475.574.7; 3.8%NA71.7; 1.2%
White miners, n=620, age=32.7 (SD 1.7), height=1.8: Predicted Knudson ECCS
 FVC (l)4.540.530.153.663.62; 4.09%3.54; 3.0%3.68; 5.3%
 FEV1(l)3.740.45−0.013.012.96; 4.9%2.98; 4.6%3.06; 6.6%
 FEV1%82.55.8−0.2773.072.7; 4.6%73.0; 5.1%71.7; 3.1%