In pregnancy, women often undergo screening to assess whether their fetus is likely to have Down Syndrome.
Question:
In pregnancy, women often undergo screening to assess whether their fetus is likely to have Down Syndrome. The screening test evaluates levels of specific hormones in the blood. Screening test results are reported as positive or negative, indicating that a woman is more or less likely to be carrying an affected fetus. Suppose that a population of N=4,810 pregnant women undergo the screening test and are scored as either positive or negative depending on the levels of hormones in the blood. In addition, suppose that each woman is followed to birth to determine whether the fetus was, in fact, affected with Down Syndrome.
The results of the screening tests are summarized below: Using this table, calculate the following:
a) the probability that a woman with a positive screening test has an affected fetus
b) the probability that a woman with a negative test has an affected fetus
c) sensitivity and specificity
d) false positive fraction and false negative fraction
e) positive predicuve value and negative predictive value
Statistics The Art and Science of Learning from Data
ISBN: 978-0321755940
3rd edition
Authors: Alan Agresti, Christine A. Franklin