- Comparison of carboxyhemoglobin values by group, smoking status, and time.
| Variables | F | DF | P-values |
| Group | 84,132 | 1 | <0.001 |
| Smoking status | 191,568 | 1 | <0.001 |
| Time | 11,707 | 11 | 0.386 |
| Group - smoking status | 7,002 | 1 | 0.008 |
| Group - time | 25,541 | 11 | 0.008 |
| Smoking status - time | 37,12 | 11 | <0.001 |
| Group - smoking status - time | 2,09 | 11 | 0.998 |
DF: degrees of freedom, F: test statistic