Coefficient of variation for adjusted and unadjusted forced expiratory flows (FEFs)
| Adjusted FEFx/FVC coefficient of variation % | Unadjusted FEFx coefficient of variation % | p-value | |
| Males | |||
| FEF25 | 19.2 | 18.3 | 0.00027 |
| FEF50 | 23.9 | 25.1 | 0.00097 |
| FEF75 | 36.0 | 38.7 | 5.81×10−5 |
| FEF25–75 | 25.4 | 27.2 | 6.23×10−7 |
| Females | |||
| FEF25 | 18.7 | 18.6 | 0.739 |
| FEF50 | 22.9 | 24.9 | 1.24×10−13 |
| FEF75 | 39.8 | 43.2 | 1.51×10−10 |
| FEF25–75 | 25.8 | 28.6 | 9.46×10−19 |
FEFx: forced expiratory flow at 25%, 50%, 75% and 25–75% of forced vital capacity (FVC).