def-incidence-rate.qmd

*New content for 2025:*

:::{#def-incidence-rate}
#### Incidence rate

Given a population of individuals indexed by $i$, 
each with their own hazard rate $\haz_i(t)$, 
the **incidence rate** for that population is the mean hazard rate:

$$\incidence(t) \eqdef \frac{1}{n}\sumin \haz_i(t)$$

:::

---

*New content for 2025:*

:::{#thm-homogenous-incidence}

#### Incidence rate in a homogenous population

If a population of individuals indexed by $i$ 
all have identical hazard rates $\haz_i(t) = \haz(t)$, 
then the **incidence rate** for that population 
is equal to the hazard rate:

$$\incidence(t) = \haz(t)$$

:::

*(End of new content for 2025)*