The combined accuracy rate for the screen to detect the chromosomal abnormalities mentioned above is approximately 85% with a false positive rate of 5%. This means that (from
americanpregnancy.org 1 )
Approximately 85 out of every 100 babies affected by the abnormalities addressed by the screen will be identified. (Positive Positive)
Approximately 5% of all normal pregnancies will receive a positive result or an abnormal level. (False Positive)
Given that your test came back negative, determine the likelihood that the child will actually have spinal bifida.
Given that your test came back negative, determine the likelihood that the child will not have spina bifida
Given that a positive test means you have a 1/100 to 1/300 chance of experiencing one of the abnormalities, determine the likelihood of spinal bifida in a randomly selected child.
You can get some help checking your arithmetic using the Bayes’ Sage interact.