How is specificity defined?

• A. The % of healthy individuals who would have a normal result
• B. The % of individuals with the target condition who would have a normal result
• C. The prevalence of the disease in the population
• D. The positive predictive value of the test

Answer: (A)

Specificity is the proportion of people without the condition who test negative. In other words, it tells you how often the test correctly yields a normal result in healthy individuals. For example, if 100 healthy people are tested and 95 have a negative result, the specificity is 95%. This is distinct from sensitivity, which measures how well the test identifies those who actually have the disease. Prevalence describes how common the disease is in a population, and positive predictive value indicates how likely a positive result truly means disease. So the statement about healthy individuals having a normal result aligns with the definition of specificity.