Table 3 Results from regression model of maximum FEV1 in relation to age, height, smoking, colliery, and dust exposure.

	Coefficient	t
Constant	4.00	137.8
Age (linear term, years)	−0.035	−28.4
Height (cm)	0.042	38.5
Smoking (v non‐smoker)
Current cigarette smoker	−0.023	−0.8
Current other smoker	0.109	1.1
Ex‐smoker	0.126	3.1
Additional age effect for:
Current cigarette smoker	−0.0078	−5.9
Current other smoker	−0.0073	−2.0
Ex‐smoker	−0.0085	−4.8
Cum exposure (gh/m3)	−0.00063	−7.4

Differences in FEV1 between collieries were allowed for but are not shown. The association between dust exposure and level of FEV1 was statistically significant whether or not the terms for colliery differences were included.

The table shows coefficient and the ratio of the coefficient to its standard error (t). Ratio values of 2 or more indicate statistical significance at the 5% level.