Introduction of interactions by dichotomising the outcome
| Interaction* | Value of the parameter indicated | |||||||
| 0.25 | 0.50 | 0.75 | 1.00 | 1.25 | 1.50 | 2.00 | 3.00 | |
| Exposure effect (βE) | ||||||||
| IA1 | 0.96 | 0.95 | 0.96 | 1.00 | 1.07 | 1.18 | 1.53 | 3.25 |
| IA2 | 0.95 | 1.00 | 1.18 | 1.53 | 2.16 | 3.25 | 8.05 | 54.8 |
| Stratum effect (βS) | ||||||||
| IA1 | 0.96 | 0.95 | 0.96 | 1.00 | 1.07 | 1.18 | 1.53 | 3.25 |
| IA2 | 1.03 | 1.11 | 1.27 | 1.53 | 1.93 | 2.54 | 4.96 | 26.1 |
| Dichotomisation cut-off on log-scale (c) | ||||||||
| IA1 | 1.38 | 1.24 | 1.11 | 1.00 | 0.90 | 0.81 | 0.65 | 0.47 |
| IA2 | 2.74 | 2.28 | 1.87 | 1.53 | 1.24 | 1.00 | 0.65 | 0.31 |
| SD on log-scale (σ) | ||||||||
| IA1 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| IA2 | 1.5*106 | 17.1 | 2.62 | 1.53 | 1.25 | 1.14 | 1.06 | 1.02 |
Unless stated otherwise, the cut-off parameter c, as well as σ, βE and βS, all equal 1.
↵* Interaction terms are labelled as indicated in table 1—that is, IA1 equals the OR associated with exposure level E=1 in stratum S=1 divided by the corresponding OR in stratum S=0, whereas IA2 equals the equivalent ratio at exposure level E=2.