Difficulty: Medium
Average Score: 72%
Simulated
Which formula should be used to calculate an incidence rate?
Correct answer
B
Rationale
The correct formula to calculate an incidence rate is B: Number of new cases in a period of time divided by the total population multiplied by a base multiple of 10. This formula is used because it calculates the rate of occurrence of new cases within a specified time frame relative to the total population, providing a measure of risk. By dividing the number of new cases by the total population, we obtain a rate that standardizes the incidence for comparison across different populations. The inclusion of a base multiple of 10 helps in expressing the rate per a specific unit (e.g., per 1000 population).
Incorrect choices:
A: This formula calculates the specificity of a diagnostic test, not the incidence rate.
C: This formula calculates the sensitivity of a diagnostic test, not the incidence rate.
D: This formula incorrectly adds old cases with new cases, which distorts the calculation of the incidence rate.
Incorrect choices:
A: This formula calculates the specificity of a diagnostic test, not the incidence rate.
C: This formula calculates the sensitivity of a diagnostic test, not the incidence rate.
D: This formula incorrectly adds old cases with new cases, which distorts the calculation of the incidence rate.