First of all, I'm not a biologist so my jargon might not exactly be common on this site. I'm a programmer and as a hobby project I try to make an algorithm that does two things:
- Determine the possible blood group and rhesus factor of a child based on the blood groups and rhesus factors of both parents.
- Determine the possible blood group and rhesus factor of an "unknown parent" based on the blood group and rhesus factors of the child and the known parent.
I found two great examples online, the "Child Blood Type Calculator" and the "Parent Blood Type Calculator" calculator on endmemo.com.
The first calculator shows some percentages of the chances. But the second calculator does only show a static answer when it comes to the blood group type and rhesus factor. According to the calculator that indicates that the rhesus factor of the "unknown parent" can only be negative when both the child and the known parent have a negative rhesus factor too.
In case the known parent and child have both RH+ the calculator shows that the unknown parent must have had RH+ as well. But isn't the statistical chance 6.25% that the unknown parent still have had RH- instead?
Secondly, how can I calculate the likelihood/chance that the unknown parent has a certain rhesus factor or blood group type? Now the calculator shows 'A/B/O' and 'RH+' when the child has 'O+' and the known parent has 'O+' but what are the chances the unknown parent has A, B or O or RH- anyway?
Side-note: I'm not related to endmemo.com.