Memorial for the Tucson Shooting of 2011 : image by nicandx (Xavier Velasquez)
Gun violence makes the news all too frequently. Do statistics help analyze gun crimes?
After tragedies such as the shootings in Newtown CT in 2012, or in Tucson in 2011, how might the advocates for gun control make their case through mathematics?
A Simple Introduction to Gun Violence Statistics
This article does not advocate for or against gun control; rather it helps explain how statistical methods can help analyze a situation.
Let’s examine a couple of sets of statistics concerning the deadly use of firearms in the United States.
First, note that these rates are “per 100,000 population”. Statisticians take this approach because it’s easier for us to understand “1.2 versus 3.4, per 100,000″ rather than counting the zeroes in “0.000012 versus 0.000034.” Both phrases carry the same information, but we can generally understand the first package more quickly.
The “mean” of a set of numbers is the average value. It equals the sum of the values, divided by the number of entries. This does not indicate that the average international firearms homicide rate is 0.72 per 100,000. The 0.72 value is merely the average of the nine rates shown. To calculate the average international value, we would need to calculate the total deaths for all the populations in those countries.
Math Formulas for Mean and Variance : Image by Mike DeHaan
The “standard deviation” is the square root of (the sum of the squares of the difference between each value and the mean, divided by the number of entries).
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