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Lupus is an autoimmune disease in which antibodies that are supposed to attack f

ID: 3158669 • Letter: L

Question

Lupus is an autoimmune disease in which antibodies that are supposed to attack foreign cells to prevent infections instead see plasma proteins as foreign bodies, leading to a high risk of blood clotting. It is believed that 2% of the population suffer from this disease. The test is 98% accurate if a person actually has the disease. The test is 74% accurate if a person does not have the disease.
If an individual has tested negative for lupus, what is the probability that this person does not have lupus. (In other words, what is the probabilty of a correct/true negative result?) Give your result to four decimal places.

Explanation / Answer

from the given data

The percentage of people suffering from disease is 2%

The percentage of people not suffering from disease is 98%

the percentage of accuracy of the test if the person has the disease is 98%

the percentage of accuracy of the test if the person doen not have the disease is 74%

The probability that this person does not have lupus or disease is =0.98*0.74 =0.7252