Table 1.
Subgroup | Group, outcome percentage | Subgroup effect (relative risk reduction) | ||
---|---|---|---|---|
Treatment | Control | |||
Category 1 | 34 | 40 | 0.15 | ↕ |
Category 2 | 22 ↔ | 42 | 0.48 | |
Category 3 | 25 | 35 | 0.29 |
The horizontal arrow indicates a within-subgroup test. The results of this test are called a subgroup effect. In our example, the test is performed for every subgroup using a χ2 test. The vertical arrow indicates a between-subgroup interaction test. The results of this test are called an interaction. It is not performed in our example.