From: CurtAdams@aol.com
Date: Wed May 29 2002 - 21:13:20 MDT
In a message dated 5/29/02 18:49:46, mail@HarveyNewstrom.com writes:
>On Wednesday, May 29, 2002, at 07:57 pm, CurtAdams@aol.com wrote:
>
>> It doesn't have to be consistent; probabilistic is enough.
>
>Wrong. People argue that blacks are more likely to commit crime. This
>does not mean that we can identify criminals by skin color.
You can't ID anybody as a criminal based on skin color; but you often
must take actions considering the *possibility* they are a criminal.
You face decisions about which side of the street to walk on, who
to watch at a store, or which exit to go out. If one ethnic group is
more likely to commit a particular form of crime, those who consider
that fact while making the decision will, on average, be victimized
less often. Likewise, they will unfairly accuse the innocent less
often.
Really, you can never ID anybody as a criminal. Based on various
forms of evidence, you can conclude somebody has a 10% or 20%
or 50% or 90% or 99.9999% chance - but you never really know
for sure.
>But you are making false assumptions. Do the math and calculate your
>error rate. If 10% of whites are criminals and 20% of blacks are
>criminals, that means your fear of a black person being a criminal is
>wrong 80% of the time. What good is a "measurement" or
>"behavioral/ability characteristic" if it is wrong four times as often
>as it is right?
It's of great value if the value of correct action is more than 4 times
the cost of incorrect inaction. Your chance of getting hit by a car when
you cross a side street without looking is less than 10% but you're
well advised to look anyway. And, if you're in a hurry, you might
run across a side street without looking but you won't a freeway.
>> No, you have to measure *something* or you can't assign a group.
>But in the first case you have directly measured traits that are
>accurate for all members of the group. In the second case you have
>unmeasured traits that are not accurate for all members of the group.
You can measure colors, sexes, etc., as well as anything. Certainly
better than whether somebody has cooperated with you in the past -
there are a gazillion ways you could have been had and not yet know
it.
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