Which formula should be used to calculate an incidence rate?
Number of true negatives/number of true negatives + number of false positives.
Number of new cases in a period of time/the total population x base multiple of 10.
Number of true positives/number of true positives + number of false negatives.
Number of new cases+ number old cases in a period of time/the total population x base multiple of 10.
The Correct Answer is B
A. Number of true negatives / (true negatives + false positives): This formula is used to calculate specificity, not incidence.
B. Number of new cases in a period of time / total population × base multiple of 10: Incidence rate measures the number of new cases of a disease occurring in a population during a specific period. It is expressed per a base population size (e.g., per 1,000 or 100,000 people) to allow for comparisons across different populations.
C. Number of true positives / (true positives + false negatives): This formula is used to calculate sensitivity, not incidence.
D. Number of new cases + number of old cases in a period of time / total population × base multiple of 10: This describes prevalence, which includes both new and existing cases, not incidence.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Agent, Host, Environment: The epidemiologic triangle consists of:
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Agent – The cause of disease (e.g., bacteria, viruses, toxins).
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Host – The person or animal affected by the disease.
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Environment – External factors that influence disease transmission (e.g., climate, sanitation, population density).
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B. Agent, Condition, Variable: "Condition" and "Variable" are not standard components of the epidemiologic triangle. The correct term is host (the affected person or animal).
C. Agent, Host, Condition: "Condition" is not part of the triangle. The environment is a crucial factor that influences the spread of disease.
D. Agent, Host, Disease: "Disease" is an outcome rather than a component of the epidemiologic triangle. The triangle focuses on the factors that contribute to disease spread, including the environment.
Correct Answer is B
Explanation
A. Reassure the student that it is just a bad cold and will soon pass: This dismisses the symptoms and delays necessary public health intervention.
B. Inform all students, staff, and faculty of a possible measles exposure: Koplik spots (small white spots inside the cheeks) are a classic early sign of measles, which is highly contagious. Prompt notification is needed to prevent an outbreak.
C. Inform all students, staff, and faculty of a possible rubella epidemic: While rubella also causes a rash, it does not present with Koplik spots.
D. Tell the student to take two acetaminophen and drink lots of fluids: Symptomatic relief is important but does not address the risk of measles transmission.
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