Table 1 A hypothetical population with positive/negative confounding U

Level of U (i)

Population number (m _i )

Positive confounding

Negative confounding

Exposure prevalence (p _i )

Disease risk among the unexposed (${\mathit{r}}_{\mathit{i}}^{\mathit{u}}$)

Relative risk (${\mathit{r}}_{\mathit{i}}^{\mathit{e}}/{\mathit{r}}_{\mathit{i}}^{\mathit{u}}$)

Exposure prevalence (p _i )

Disease risk among the unexposed (${\mathit{r}}_{\mathit{i}}^{\mathit{u}}$)

Relative risk (${\mathit{r}}_{\mathit{i}}^{\mathit{e}}/{\mathit{r}}_{\mathit{i}}^{\mathit{u}}$)