Bap, these are expectations. This analysis is valid if you are willing to draw expectations from the data, as Patrick originally did. This is done in the same manner as how the National Weather Service advertises the odds of getting struck by lightning to be 1E-6 in a given year--they do so by dividing the number of strikes per year by the total population. Does that mean those are the odds that YOU will get struck by lightning? Doubtful--I don't know how you spend your time. If you play golf on mountaintops during thunderstorms, the likelihood will be far greater than if you live inside a subterranean Faraday cage. But for large samples of a large population, that expectation can be applied with reasonably good agreement.
People DO do the same math with the NBA, NFL, and MLB; those statistics ARE part of the equation in sports management decisions (too much so for Brad Pitt, in Moneyball). Future expectations are based on prior performance, but just like with roulette, quantum mechanics, and women, there are no certainties.
Marcus, I agree with your math, but it doesn't seem to disagree with mine. Given you are white, the data suggests that the probability of being murdered by someone who is black is 2E-6 or 2/1,000,000, not 2E-5.
And this data is gathered over a year, so these are expectations that this will occur within a given year. Specifically, the data is from 2010.
I think your analysis of the data is not quite right, Patrick. Your statement "white people are much more likely to be murdered by black people in the US than vice versa" seems to disagree with what the data suggests.
I wrote a quick Python script to calculate some expectations given the FBI data you posted, and an assumed population of 308,645,538 (from the 2010 census).
This obviously does not try to address bias in conviction rates or any other imperfections in the data.
The outputs are copied and pasted below:
Regardless of your race:
Your odds of being murdered: 2.035333058e-05
Your odds of being murdered by a white: 9.91755223358e-06
Your odds of being murdered by a black: 9.55479395463e-06
Given you are white:
Your odds of being murdered: 1.48837903769e-05
Your odds of being murdered by a white: 1.2423290014e-05
Your odds of being murdered by a black: 1.99971574947e-06
Given you are black:
Your odds of being murdered: 6.99193961705e-05
Your odds of being murdered by a white: 5.60383395778e-06
Your odds of being murdered by a black: 6.32102188174e-05
So, if you are white, your odds of being murdered by a black are about 2 in one million. If you are black, your odds of being murdered by a white are about 2.8 times that, or 5.6 in one million.
If you are black, you are about 4.7 times more likely to be murdered than if you are white.