Calculadora de Riesgo Relativo Gratis
Calcula el riesgo relativo comparando la incidencia de un evento entre dos grupos de estudio.
Relative Risk (RR)
2.0000
Relative Risk (RR) vs Group 1 - Event (a)
Fórmula
## How to Calculate Relative Risk ### Formula **RR = [a / (a+b)] / [c / (c+d)]** Relative risk compares the probability of an event in the exposed group to the probability in the unexposed group. RR = 1 means no difference. RR > 1 means higher risk in the exposed group. RR < 1 means the exposure is protective. The Number Needed to Treat (NNT) = 1 / |Risk Difference|.
Ejemplo Resuelto
Group 1: 30 events out of 100. Group 2: 15 events out of 100.
- 01Risk Group 1 = 30 / (30+70) = 30/100 = 0.30
- 02Risk Group 2 = 15 / (15+85) = 15/100 = 0.15
- 03RR = 0.30 / 0.15 = 2.0
- 04Risk Difference = 0.30 - 0.15 = 0.15
- 05NNT = 1 / 0.15 ≈ 6.67
- 06Group 1 has twice the risk; for every ~7 people treated, one event is attributable to exposure.
Preguntas Frecuentes
When is relative risk preferred over odds ratio?
RR is preferred in cohort studies and randomized trials where incidence can be directly measured. Odds ratios are used in case-control studies where incidence cannot be determined. For rare events, OR approximates RR.
What is the difference between relative risk and absolute risk?
Relative risk is the ratio of two risks (multiplicative comparison). Absolute risk difference is the subtraction of two risks (additive). Both are needed: a large RR with tiny absolute risk may not be clinically important.
What does NNT mean?
Number Needed to Treat is the number of patients who must receive a treatment for one additional patient to benefit (or be harmed). Lower NNT means a more effective treatment. NNT = 1/|Risk Difference|.
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