From: djohns@elm.circa.ufl.edu (David A. Johns)
Newsgroups: soc.culture.african.american
Subject: Re: Violent crime stats from a reliable source
Date: 18 Aug 92 16:05:43 GMT
Organization: University of Florida, Gainesville

[I didn't get the original posting here, so I'm taking these quotes
from Charles Isbell's response.  Sorry if I missed any relevant
context.]

trs4742@sigma.tamu.edu (SEBESTA, TIMOTHY RICHARD) writes:
# First of all, something interesting was that 89% of white violent
# offenders victimized other whites,while 49% of Black violent
# offenders victimized other Blacks.

These are pretty useless numbers.  What they mean depends on how
they were determined.

First, if it's *by conviction* (i.e., in "solved" cases, in 89% of
the cases where the victim was white the criminal was white, etc.),
then the arrest and conviction rates of blacks and whites are
relevant, and may vary for many reasons -- not only bias in the
judicial system, but the fact that white neighborhoods are likely
to be better patrolled, blacks are more conspicuous in a white
neighborhood (than whites are), etc.

Second, if it's by *criminal* (e.g., interviews with convicted
criminals), all the above problems are still relevant, plus the
question of the number of crimes each interviewee committed.  The
figures could be misleading if the question was "have you ever
committed a violent crime against a member of another race".

And third, if the survey is by *victim*, there must be a huge
"unknown" factor that might well not be evenly distributed between
possible categories of criminals.

# I'm not siding with anyone, but uniform crime reports gathered
# statistics from across the U. S. and their report showed that 94%
# of crimes against blacks are committed by blacks. 85% of crimes
# committed against whites are by other whites.

The first figure seems to disprove the belief common among whites that
blacks are more of a threat to them than whites, but, as Charles
pointed out, they say nothing about the prevalance of criminal
behavior in each group.  Two critical pieces of evidence are missing.
First, the victimization rate of each group -- if blacks are
victimized twice as much as whites, for instance, then the 6% of
crimes against blacks committed by whites becomes a much larger
number, maybe not statistically different from the 15% of crimes
committed against whites by blacks (simplifying the categories to just
black and white).

The second factor relevant to the percentage of criminals in each
community is the number of crimes committed by each individual.  If
"career criminals" are more prevalent among blacks, for instance, a
higher number of crimes could be accounted for by a lower percentage
of the population.

# I've done alot of research in this area and have a paper up for
# publication in the near future. If you have anymore questions
# concerning violent crimes, I may be able to help.

I'm interested -- especially in the methodological aspects.  I'm
becoming more convinced every day that percentages are America's new
religion.  The government, news media, and individuals all throw them
around as if they bore some inherent meaning.

As a net signature I saw once said: You can prove anything with
numbers -- but not to a statistician.

David
Newsgroups: soc.culture.african.american