If a breast cancer screening test accurately identified 80 out of 100 individuals free from breast cancer, what is the specificity of this test?

Specificity measures the ability of a test to correctly identify individuals who do not have a particular condition—in this case, breast cancer. It is calculated using the formula:

Specificity = (True Negatives) / (True Negatives + False Positives)

In this scenario, the test accurately identified 80 out of 100 individuals free from breast cancer. This means that there are 80 true negatives (correctly identified as cancer-free). If 100 individuals were tested and 80 were correctly identified as free from cancer, it’s implied that the remaining individuals (20 in this case) would be either false positives or might represent cases with cancer that were not part of this count.

Since we focus solely on the individuals who are cancer-free in this calculation—those that the test correctly identified—the total of cancer-free individuals (true negatives) is 80 out of 100.

To calculate specificity, we proceed as follows:

• True Negatives = 80

• False Positives = 0 (since we assume all others are correctly classified as having cancer or not within the scenario provided)

Now we plug into the specificity formula:

Specificity = 80 / (80 + 0) = 80 / 80 = 1 or