From a 2x2 contingency table, which pairing gives the number of people with the condition?

From a 2x2 contingency table, which pairing gives the number of people with the condition?

• A. True positive and false negative.
• B. False positive and true negative.
• C. True positive and true negative.
• D. False positive and false negative.

Answer: (A)

In a diagnostic 2x2 table, to know how many people actually have the condition, add those who truly have it regardless of their test result. True positives are people who test positive and do have the condition, while false negatives are people who have the condition but test negative. Adding these two groups gives the total number of individuals with the condition. The other pairings don’t represent those with the condition: false positives and true negatives are people without the condition, true positives plus true negatives are all correct test outcomes, and false positives plus false negatives are all incorrect test outcomes. So the correct pairing is true positives and false negatives.

In a diagnostic 2x2 table, to know how many people actually have the condition, add those who truly have it regardless of their test result. True positives are people who test positive and do have the condition, while false negatives are people who have the condition but test negative. Adding these two groups gives the total number of individuals with the condition.

The other pairings don’t represent those with the condition: false positives and true negatives are people without the condition, true positives plus true negatives are all correct test outcomes, and false positives plus false negatives are all incorrect test outcomes.

So the correct pairing is true positives and false negatives.