From an article on gun violence and legislative restrictions on firearms, found via AQF. The article shows how to do correlation right—with graphs, with several dimensions of analysis, and with very little interest for the correlation coefficients or the p-values themselves. A nice example of the intra-ocular trauma test.
Last year, I had the idea of using the Allourideas pairwise comparison software to crowdsource a ranking of countries by their degree of “democracy” in 2010. I asked students in my Dictatorships and Revolutions class to set the ball rolling, and then posted the link to the widget here, allowing anybody to vote. Surprisingly, in just a couple of months of voting the results were interestingly close to standard indexes of freedom or democracy: the crowdsourced ranking had a correlation of 0.84 with Freedom House’s widely-used ratings of political and civil liberties for 2010, and the basic crowdsourced ranking was generally plausible (see this post for further analysis of these results) . In fact, by now the correlation has increased to 0.86 (8556 votes total), which is about as good the correlation between Freedom House and Polity IV (0.87).Abandoned Footnotes: Crowdsourcing a Democracy Index – 2012 edition
“Think about it. Imagine how strong the “true” relationship must be if it shows up even when using only rough proxies for the “true” levels of inequality and immobility. In light of Winship’s criticisms, the high correlation in this chart is all the more remarkable. If his gripes are correct, then graph understates the correlation between inequality and mobility.” (via Freakonomics » Is Higher Income Inequality Associated with Lower Intergenerational Mobility?)