My casual jeremiad writ large.
Jul. 28th, 2008 09:17 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
intersticehttp://www.latimes.com/news/local/la-me-dna20-2008jul20,0,1506170,full.story
I remember using this very example in my stats class last summer. Basically, even though in one sample a certain (combination of) gene(s) may have 1-in-a-billion chance of showing up at random (i.e. a false positive match), that sample may not be representative. For example, the gene may be more common in the Amish thus increasing the false positive rate. One 14-year-old overachieving Chinese student expressed concern about allowing too much freedom for the defense in a legal argument. She also didn't like my reductionist equation of intelligence to reasoning speed (I used this example for a brief and casual lecture on generalized linear models I think); she may have been right there, actually.
The genetics is a little more interesting than just that. You'd like your claims to be "conservative"; that is, the actual chance to be even smaller than you claim. However, in this case it always seems possible that there will be some isolated group of people who may have certain common genes. So do we actually model population flows and take the argument one level higher, making arguments about distributions of genes themselves being unlikely? Should we allow this reasoning in court, having seen the travesty of explanation that even basic DNA testing provokes? But then maybe it's been so hard because people have had an intuitiveunderstanding and suspicion of exactly what's going wrong now!
If not, do we throw everything out, or instead of trying to "do it right" fall back to our flawed and incomprehensible zeitgeist to make our decision for us?
Or is there even a deeper distinction between an unlikely individual within a population (legally admissible argument) and an unlikely population (inadmissible)?
I remember using this very example in my stats class last summer. Basically, even though in one sample a certain (combination of) gene(s) may have 1-in-a-billion chance of showing up at random (i.e. a false positive match), that sample may not be representative. For example, the gene may be more common in the Amish thus increasing the false positive rate. One 14-year-old overachieving Chinese student expressed concern about allowing too much freedom for the defense in a legal argument. She also didn't like my reductionist equation of intelligence to reasoning speed (I used this example for a brief and casual lecture on generalized linear models I think); she may have been right there, actually.
The genetics is a little more interesting than just that. You'd like your claims to be "conservative"; that is, the actual chance to be even smaller than you claim. However, in this case it always seems possible that there will be some isolated group of people who may have certain common genes. So do we actually model population flows and take the argument one level higher, making arguments about distributions of genes themselves being unlikely? Should we allow this reasoning in court, having seen the travesty of explanation that even basic DNA testing provokes? But then maybe it's been so hard because people have had an intuitive
If not, do we throw everything out, or instead of trying to "do it right" fall back to our flawed and incomprehensible zeitgeist to make our decision for us?
Or is there even a deeper distinction between an unlikely individual within a population (legally admissible argument) and an unlikely population (inadmissible)?
