MCAT® ExamCritical Analysis and Reasoning SkillsEasy
A team of researchers is developing a new diagnostic test for a rare disease. They conduct a study where 100 individuals known to have the disease and 100 healthy individuals are tested. The test correctly identifies 95 of the diseased individuals and incorrectly identifies 5 of the healthy individuals as having the disease. Which of the following best describes the ability of the test to correctly identify individuals who do not have the disease?
- ANegative Predictive Value
- BSpecificity
- CSensitivity
- DPositive Predictive Value
Show answer & explanationAnswer & explanation
Correct answer: B. Specificity
Specificity measures the proportion of actual negatives that are correctly identified as such. In this case, it refers to the test's ability to correctly identify healthy individuals.
Why the other options are wrong
- A. Negative Predictive Value is the probability that subjects with a negative test result actually do not have the disease.
- C. Sensitivity measures the proportion of actual positives that are correctly identified.
- D. Positive Predictive Value is the probability that subjects with a positive test result actually have the disease.
Specificity
Specificity is a measure of a diagnostic test's ability to correctly identify individuals who do NOT have the condition (true negatives).
- Calculated as True Negatives / (True Negatives + False Positives)
- High specificity means a low rate of false positives
- Crucial for confirming the absence of a disease
Memory trick: SENsitive people get POSITIVE results, SPECific people get NEGATIVE results.