NR 442 Week 6 ELO: Interactive Exercise – Epidemiology Define epidemiology. There are two principal types of epidemiology: (1) analytic epidemiology and (2) descriptive epidemiology. Describe each. Explain the epidemiological triangle model of agent-host-environment, Wheel Model and the web of causation model. Describe the concept of risk. How do you calculate rates? Morbidity rates refer to rates of illness in a defined population. The two primary morbidity rates are incidence rates and preva...