Question

A new screening test for a disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Four hundred (400) people are screened at a clinic during the first year the new test is implemented. (Assume the true prevalence of the disease among clinic attendees is 10%.)Calculate the following values11) The number of false positives is:A. 108B. 132C. 24D. 252

Answer 1

The number of false positives is 108. The right answer is A

Explanation:

According to the given data we have the following:

probability of negative results which are correcly identified =0.7

probability of negative results which are wrongly identified =1-0.7 =0.3

hence, probability of negative result = 1-0.1 =0.9

Therefore, in order to calculate the number of false positives we would have to use the following formula:

false positives =total number * probability of negative results which are wrongly identified * probability of negative result=400 * 0.9*(1-0.7) = 108

false positives = 400 * 0.9*(1-0.7)

false positives = 108

The number of false positives is 108