Odds Squad: Change the Odds
Risk = % with. Odds = with ÷ without.
RR: "For a given sample size, group A will have __ times as many outcome cases as Group B."
OR: "The ratio of outcome cases to not outcome cases in Group A is __ times the ratio in Group B."
Group A
0/100 with outcome
Risk in Group A 0%
Group B
0/100 with outcome
Risk in Group B 0%
Prob. of outcome (risk)Just the percent with the outcome!
A: — B: — RR: —
Odds of outcomeOdds = (# with outcome) ÷ (# without outcome)
A: — B: — OR: —
Outcome + Outcome − Total
Group A — — —
Group B — — —
Column total — — —
When the outcome is rare, RR and OR are similar. As the outcome becomes common, notice how the odds ratio grows faster than the relative risk.