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anka

A screening test is developed to identify hearing disabillity in infants. It is first tried in 2 separate hospitals. However, among those who tested positive with this new test, the rate of false positive tests at hospital A are significantly lower than the rate at hospital B. What is the likely explanation?

A. the specificity of the test is lower in hospital B
B. the sensitivity of the test is lower in hospital A
C. the prevalence of disease is higher in hospital A
D. cannot be determined
E. error in measurement

grzybcia

anka

niestety C, wyjaśniają to tak:

The sensitivity and specificity of the test are unique to the test
and do not vary if the tests are identical. However both the positive and negative predictive value of the test can vary with the population.Therefore if the same test is being employed in 2 separate populations, the reason for a discrepancy in the rate of false-positive tests could be due to differences in the prevalence of the disease in the 2 separate populations. In particular, the higher the prevalence the lower the rate of false-positive tests.