Risk Ratio Calculator
The Risk Ratio Calculator computes the risk ratio (incidence rate ratio) between exposed and unexposed populations. Calculate attributable risk and population attributable fraction to quantify the public health impact of risk factors.
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What is a Risk Ratio?
A risk ratio (also called incidence rate ratio) compares the incidence of an outcome in an exposed group to that in an unexposed group. It is mathematically identical to relative risk when calculated from cumulative incidence data. RR = 3.0 means the exposed group has 3 times the incidence rate of the outcome.
Risk ratios are preferred in public health because they directly communicate the fold-increase in disease risk. Combined with attributable risk (AR = risk_exposed - risk_unexposed), they quantify both relative and absolute disease burden from an exposure.
Формулы и Используемые Уравнения
В калькуляторе заложены 5 основных уравнений:
1 Risk Ratio ▼
Exposed rate: 15 per 1000. Unexposed rate: 5 per 1000. RR = 15/5 = 3.0.
2 Attributable Risk ▼
AR = 15/1000 - 5/1000 = 10/1000. The exposure accounts for 10 extra cases per 1000.
3 Population Attributable Fraction ▼
If 30% of population exposed and RR = 3: PAF = 0.3×2 / (1+0.3×2) = 0.375 = 37.5%.
Как Пользоваться Калькулятором
Чтобы использовать этот Калькулятор Отношений, выполните 3 простых шага:
Введите Данные
Введите известные числа в поля ввода. Оставьте одно поле пустым — калькулятор вычислит это неизвестное значение.
Выберите Режим
Выберите режим работы — Решение пропорций, Упрощение отношений или Масштабирование. В каждом режиме используются свои математические формулы.
Получите Результат
Нажмите кнопку Вычислить. На экране отобразится ответ с цветной шкалой отношения, круговой диаграммой и пошаговым решением.
Примеры Задач с Пошаговыми Решениями
Вот 3 практических примера расчетов с подробным математическим описанием действий:
Ввод 1 Disease rates: 20/1000 exposed vs 5/1000 unexposed
Ввод 2 Calculate PAF: 40% exposed, RR = 2.5
Ввод 3 Protective factor: vaccinated risk 3%, unvaccinated 12%
Часто Задаваемые Вопросы
How is risk ratio different from odds ratio? ▼
Risk ratio uses incidence proportions: events/total. Odds ratio uses odds: events/non-events. For rare outcomes (< 10%), OR ≈ RR. For common outcomes (> 10%), OR overestimates the strength of association compared to RR.
What does attributable risk tell us? ▼
Attributable risk (AR) is the absolute difference in risk between exposed and unexposed groups. It tells you how many additional cases per unit of population are caused by the exposure, which is useful for public health resource planning.
What is population attributable fraction? ▼
PAF estimates the proportion of disease in the total population that would be prevented if the exposure were eliminated. A PAF of 37.5% means eliminating the exposure would prevent 37.5% of all cases.
Can risk ratio be calculated from case-control studies? ▼
No. Case-control studies sample by outcome status, making the denominator (total exposed/unexposed) unknown. Use odds ratio instead. Risk ratio requires cohort data where you follow groups forward in time.
What is a clinically meaningful risk ratio? ▼
Context matters. In oncology, RR = 0.80 (20% reduction) may be significant for a deadly cancer. In preventive medicine, RR = 0.50 (50% reduction) is typically considered clinically meaningful. Always report alongside AR and NNT.