The question says, "You are trying to estimate the likelihood that a fetus of a first-time mother has Trisomy 21." So that's the thing you don't know. You do know the mother's age.
Tom
The question says, "You are trying to estimate the likelihood that a fetus of a first-time mother has Trisomy 21." So that's the thing you don't know. You do know the mother's age.
Tom