Violence in St Louis

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Clarissa

September 15, 2015

Watching the local news in St Louis is like receiving reports from a war zone. A woman is shot in her car. A mother of five is shot and killed. A family of four is robbed at gunpoint.

St Louis is one of just a couple of cities where there has been a real (as opposed to imagined by scandal-monging media) spike in violent crime. I wouldn’t attribute it to any specific events because there is always a spike in crime in St Louis. The authorities are making heroic efforts to make the city more habitable but the progress is slow and uneven.

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4 responses to “Violence in St Louis”

Vic Crain

September 15, 2015

Current statistics don’t support “imaginary.” St. Louis was mentioned in this article, but wasn’t considered a particular hot spot. Baltimore this year has more murders than NYC, despite being substantially smaller. http://www.usatoday.com/story/news/2015/07/09/us-cities-homicide-surge-2015/29879091/

The pattern is inconsistent. My belief is that cities with better social service programs are having fewer problems, but that’s hypothesis at this point.

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1. Clarissa
  
  September 15, 2015
  
  Nate Silver says the spike in violence is limited to just a couple of places. And St Louis is among the worst. His analysis tends to be very careful.
  
  http://fivethirtyeight.com/features/scare-headlines-exaggerated-the-u-s-crime-wave/
  
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  1. Vic Crain
    
    September 15, 2015
    
    “Lies, Damned Lies and Statistics” was the title of a book from which I taught many years ago. Their effort to gather data is admirable; the statistical analysis isn’t. From what I can gather from the article, they used something along the lines of a t test to determine the likelihood of getting the number of 2015 homicides as a simple matter of random variation.
    
    What’s wrong with that?
    (1) Applying sampling statistics to non-sample data. We’re dealing with actual counts of what happened. There’s no sampling error involved.
    (2) We know there is bias in reporting of statistics. The t test assumes accurate reporting without bias. It cannot deal with bias. The test in fact assumes a normal distribution around the mean and that would be highly unusual for population data. The test also assumes a common underlying rate for all cities, which is simply not true. Without that assumption, there’s nothing to calculate.
    (3) The t test ignores context. What makes the data especially interesting is that rates were in decline prior to this year in most of these places.
    
    A better approach would be to build a time series model separately for each city for which data is available. There’s no evidence they did that. Such a model would include demographic and ecnomic data and would be much more interesting than what they did. However, it might not show what they want.
    
    Now a simple test as to whether a community has a problem is this:
    
    (1) Assume there is an equal probability that crime will increase or decrease in a community each month. For simplicity, we’ll ignore the no change alternative.
    
    (2) Thus there’s a 50% chance of crime increasing in any give month. The odds of an increase in 2 consecutive months would be 25% (.5 x .5) and in 3 consecutive months 12.5% (.5 x .5 x .5), etc. By the time you get to five months, you’re seeing a result that’s rather improbable — and you had better be thinking about why its happening.
    
    Right now, I suspect there are real problems in a number of cities. At best, my position favors the Scottish verdict of “Not Proven.” I don’t believe the data support use of the term imaginary.
    
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Matt

September 16, 2015

The reason it is being denied in the 5-10 urban core’s where it is happening is highly political… I think you can piece together what agenda might be on the line..

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