Table 3. Regression equations, coefficient of determination (r²), and lower limits for spirometric variables in Black males.

Type of equation	Height coefficient	Age coefficient	Constant	r2	Lower limit
Linear
FVC, l	0.048	−0.019	−2.931	0.52	P − 0.78
FEV1, l	0.033	−0.024	−0.989	0.57	P − 0.76
FEV1/FVC, %	−0.134	−0.189	112.0	0.26	P − 8.70
PEF, L/s	0.059	−0.048	1.903	0.24	P − 2.67
Logarithmic
FEF25-75%, L/s	−	−0.670	3.735	0.42	P × 0.62
FEF50%, L/s	−	−0.517	3.383	0.30	P × 0.62
FEF75%, L/s	−	−0.956	3.872	0.50	P × 0.57

P: predicted. Linear equations: height × coefficient − age × coefficient ± constant. Example: FVC = height × 0.048 − age × 0.019 − 2.931 Logarithmic equations: natural log ^{(log height × coefficient - log age × coefficient ± constant)}. Example: FEF_25-75% = 2.7183^{( − log n age × 0.670 + 3.735)}.