Final answer:
The incidence rate is calculated by dividing the number of new cases by the number at-risk population during a time period and then multiplying by 1000. This rate helps to express the amount of new cases per 1000 individuals in a population.
Step-by-step explanation:
The formula to calculate the number of people newly diagnosed with a disease during a given time period per 1000 population at risk is known as the incidence rate. To calculate this rate, you divide the number of new cases by the number at-risk population during the time period and multiply the result by 1000 to express it per 1000 individuals.
For instance, if there are 50 new cases of a disease in a year in a population of 10,000 at risk, the incidence rate would be (50 ÷ 10,000) × 1000, which equals 5 per 1000 population at risk per year.
It's important to note that incidence rate differs from prevalence rate, which accounts for all existing cases (new and old) during a timeframe. Epidemiologists use these rates to determine the frequency of a disease and to allocate resources effectively.