TABLE 3

Fit of model type per age group and sample set

Model and age group	Primary sample		Cross-validation sample
Model and age group	Adjusted R²	see mL·min⁻¹	Adjusted R²	see mL·min⁻¹
Linear model
All	0.55	572.89	0.54	487.84
≤20 years	0.71	560.65	0.81	528.86
>20 years	0.50	574.43	0.37	484.56
Polynomial model
All	0.56	566.20	0.57	476.72
≤20 years	0.71	548.80	0.82	456.03
>20 years	0.51	568.37	0.38	478.26
Additive model
All	0.57	556.50	0.57	473.15
≤20 years	0.76	495.18	0.84	420.72
>20 years	0.52	563.82	0.38	476.92

see: standard error of the estimate.