Tuesday, April 29, 2008

Tuesday Statisticz: Dog Parks and City Safety

I wanted to see if parks had any correlation with city safety. My a priori expectation was that more parks would make a city safer, because I normally think of park goers as law abiding citizens. But then I happened upon this chart showing the number of dog parks in various cities, which I thought was even cooler. So I went back to these old crime statistics from 2006 (the "offenses known to law enforcement") and correlated the amount of crime in US cities with the number of dog parks in them. Here is a chart showing dog parks versus property crime:

Each of the dots represents one city, with a distinct crime rate and number of dog parks per capita. As you can see, r square here is nonexistent. There is no correlation. Next, here's dog parks versus violent crime:

I couldn't combine these charts because the y-axis values of the two data sets are so different, since there are many more property crimes than violent ones. In this chart, there appears to be an inverse relationship, although it is small, with an r square of merely 0.023. But is it significant? A student's t-test (t=1.18, p > .05) tells us no. So for all intents and purposes, there's nothing going on here.

Finally, just for fun, dog parks and arson:

Once again, there is nothing of importance here. Although I do like that shade of orange.

What can we draw from these statistics? For one thing, maybe a park isn't as effective a way to reduce crime as I had assumed. I suppose that growing up in picnic-central Mill Valley may have created this perception.

Also, this data gives us no reason to suspect that a dog owner will be any less likely to burn your house down than anybody else. So the next time you see your neighbor walking his dog down the street and think nothing of it, check to make sure he has no lighter fluid on him. If he does, even if it is ostensibly "for the barbecue at the Anderson's", you should be afraid. Very, very afraid.