Differentiate between sensitivity and specificity.

Differentiate between sensitivity and specificity.

• A. Sensitivity = true positives / all actual positives; Specificity = true negatives / all actual negatives.
• B. Sensitivity = true negatives / all actual negatives; Specificity = true positives / all actual positives.
• C. Sensitivity = false positives / all actual positives; Specificity = false negatives / all actual negatives.
• D. Sensitivity = overall accuracy; Specificity = likelihood ratio.

Answer: (A)

The main idea here is how a test performs among people who actually have the disease versus those who do not. Sensitivity is the proportion of true positives among all people who truly have the disease, meaning true positives divided by all actual positives. Specificity is the proportion of true negatives among all people who are disease-free, meaning true negatives divided by all actual negatives. So the best description is: sensitivity equals true positives divided by all actual positives, and specificity equals true negatives divided by all actual negatives. The other options mix up these concepts, swap what is being counted, or refer to different performance metrics altogether (like overall accuracy or likelihood ratios).

The main idea here is how a test performs among people who actually have the disease versus those who do not. Sensitivity is the proportion of true positives among all people who truly have the disease, meaning true positives divided by all actual positives. Specificity is the proportion of true negatives among all people who are disease-free, meaning true negatives divided by all actual negatives. So the best description is: sensitivity equals true positives divided by all actual positives, and specificity equals true negatives divided by all actual negatives. The other options mix up these concepts, swap what is being counted, or refer to different performance metrics altogether (like overall accuracy or likelihood ratios).