Question

A graph of a normal blood sugar level curve and a diabetic blood sugar level curve was shown, with an area seen overlapping towards the normal glycaemic curve and a cut-off point marked at 120 mg/dL. What does that overlapping area represent?

• A. True positive
• B. False positive
• C. True negative
• D. False negative

Hint:

Diseased people whose value falls below the cut-off and are called negative are which category?

Answer 1

The Correct Option is D

This problem maps an overlap region on two bell shaped glucose distributions to a screening test category. Picture the diseased (diabetic) curve sitting at higher glucose values and the healthy curve at lower values, with a vertical decision line at $120$ mg/dL. People to the right of this line are screened positive and those to the left are screened negative. The four outcome boxes follow from combining true disease status with the screening label. The region described in the stem belongs to the diabetic distribution yet spills over to the left of the cut-off, into the normal glycaemic zone. That means these individuals genuinely have diabetes but their reading fell below the threshold, so the test calls them negative. A diseased person labelled negative is by definition a false negative, the group that a screening programme dangerously misses. The companion errors would be normals pushed to the right (false positives), while correct calls give true positives and true negatives. Hence the shaded overlap is the false negative fraction. \[\boxed{\text{False negative}}\]