Summary statistics for cohort and case-control studies: cohort study
| Explanatory variable (risk factor) | Outcome variable (future disease) | Total | |
| +ve | −ve | ||
| +ve | a | b | a+b |
| −ve | c | d | c+d |
| Total | a+c | b+d | N=a+b+c+d |
Relative Risk=(a/(a+b))/(c/(c+d)). Odds ratio=(a/b)/(c/d)=ad/bc