Lisa is 40 and pregnant for the first time. As a "mature" mother, she is worried about the possibility of having a baby with Down Syndrome. Chances of a 40-year old mother having a baby with Down Syndrome is 1 in 100. Just to be on the safe side, Lisa decides to have a maternal blood serum test to check for chromosomal abnormalities. If the baby has Down Syndrome, then the blood serum test will deliver a positive result 86% of the time. There is, however, a small "false positive" rate of 5%. Lisa's blood serum test provides a positive result for Down Syndrome. What is the prior probability that Lisa's child will have Down Syndrome? What is the posterior probability that Lisa's child will have Down Syndrome?

Question

Quizplus · Accepted Answer

The Answer of Lisa is 40 and pregnant for the first time. As a "mature" mother, she is worried about the possibility of having a baby with Down Syndrome. Chances of a 40-year old mother having a baby with Down Syndrome is 1 in 100. Just to be on the safe side, Lisa decides to have a maternal blood serum test to check for chromosomal abnormalities. If the baby has Down Syndrome, then the blood serum test will deliver a positive result 86% of the time. There is, however, a small "false positive" rate of 5%. Lisa's blood serum test provides a positive result for Down Syndrome. What is the prior probability that Lisa's child will have Down Syndrome? What is the posterior probability that Lisa's child will have Down Syndrome?

Lisa Is 40 and Pregnant for the First Time