Friday

February 27, 2015

February 27, 2015

Posted by **jessie** on Sunday, May 16, 2010 at 10:05am.

The commonly used test to assess Down's syndrome risk in the unborn foetus is the 'triple test', which combines maternal age with other markers of foetal and maternal health from a single blood test. The test has a 65% detection rate, and a 5% false positive rate. Incidence of Down's syndrome in births from 35 yr old mothers is 1 in 250. The triple test from one 35 yr old mother returns a positive result. What is the probability that her foetus has Down's syndrome?

- math -
**drwls**, Sunday, May 16, 2010 at 11:45amOut of a random sample of 35 year old mothers:

Probability of false positive = (249/250)*0.05 = 0.0498

Probability of correct positive = (1/250)*0.65 = 0.0026

Probability of false negative (undetected Down's) = (1/250)*0.35 = 0.0014

Probability of correct negative = (249/250)*0.95 = 0.9462

For the woman in question, she is either a false positive or a correct positive.

Probability of Down's = (.0026)/(.0026+.0498) = 0.04962

That equals a probability of 1 in 20.2

**Answer this Question**

**Related Questions**

Statistic - Case 6.4 Maternal Serum Screening Test for Down syndrome Please ...

Statistics - One of my classmates ask this question and it wasn't answered so ...

Biology- Human Karyotyping - Could someone help me find 2 disorders that are the...

math - Samantha has an average of 92% on tree math test. If one of her grades ...

tax income - To be a qualifying child, the taxpayer must meet three general ...

statistics - An athlete suspected of having used steroids is given two tests ...

tax income - To be a qualifying child, the taxpayer must meet three general ...

English - Identify the correct sentence. A. In order to assess you're level of ...

Statistics - Which one of the following test is used to compare five means, ...

MATH Prob. - Jack is taking a four-item true–false test. He has no knowledge ...