Tag Archive: statistics


In case you haven’t heard, the North Carolina General Assembly has run amok.

It’s hard to believe that things could get worse: the last NCGA approved Ammendment One, which declared that straight marriage was the only recognized family. And they tried to outlaw accelerating sea level rise by declaring that straight lines were the only recognized graph.

And yet after the 2012 election, things turned upside down.

  • Senator Tom Tucker displayed amazing arrogance and unfamiliarity with his job description when he told a reporter: “I am the senator, you are the citizen. You need to be quiet” (Huffington Post)
  • A House resolution was proposed which would allow the establishment of a state religion, as well as incorporating prayer as a public institution (WRAL)
  • Another bill was proposed to criminalize womens’ nipples. (DTH)
  • The budget committee has considered making ends meet by closing NC’s public universities (a tactic known as, ‘eating your seed corn’) (N&O)
  • The Senate has passed a bill rolling back 40 years of environmental protections in order to make way for fracking, in defiance of the state Department of Environment’s recommendations. (McClatchyDC)

That’s just some of the more bizarre social experimentation going on; there’s been plenty of garden-variety attacks on voting rights, public education and social services for the poor.

The point of all this is, a lot of people are justifiably annoyed. So much so, that weekly protests at the state capitol have broken out, headed by the state NAACP and dubbed ‘Moral Mondays’. Peaceful protesters have been arrested by the score, then the hundred, for voicing their disgust with a runaway legislature.

Conservatives have fought back, and some have fought dirty. In one especially skeezy move, the right-wing Civitas Institute has published a public database of information on the protesters, including their photograph, and city of residence. It’s creepy, but now that it exists, it’s a window into what is happening on Moral Mondays.

The Civitas data record a total of 457 arrests. Of these, all but 8 gave their residence as in North Carolina. That is to say, 98% of the arrested are clearly locals. This data reinforces an earlier survey which found the same proportion in the protesters as a whole. This matters because some, including governor Pat McCrory have tried to dismiss the protests as the work of outside agitators.

Something disappointing about the Civitas effort is that the infographics provided are drab and at times completely inappropriate. (I mean, really?)

To show them how it’s done, let’s map out some information. Here are the absolute number of arrests, categorized by county and by city. Unfortunately, the city data which were available from the NC DOT did not have all of the cities in the arrest data, leading to 65 of 85 cities being represented in the map, explaining why some counties (eg, Cherokee) report arrests but contain no cities reporting arrest. This may introduce a bias in which smaller cities and towns are not represented when city-based data are used.

Words

Fig 1a. Moral Monday arrests, binned by county.

Words

Fig 1b. Moral Monday arrests, binned by city

Composite

Fig 1c. Composite map of 1a and 1b.

A few things seem to pop out: Arrests are geographically centered around the Triangle (Chapel Hill, Durham, and Raleigh), with other major centers around cities (eg, Charlotte, Wilmington, and Asheville). Comparing to other political maps (such as Amendment One or the 2012 presidential election), this pattern is not surprising, however, why it is happening is less clear.

Continue reading

I love graphs – my eyes quickly glaze over at a table of numeric data, but a graph, used correctly, can quickly and easily tell the whole story.

‘Used correctly’ is the key phrase – for all their power, graphs are infamously easy to bungle, and when used incorrectly they can misinform – or lie outright.

I’m going to look at an example that touches on a few graphical and statistical concepts near and dear to my heart, as well as carbon geochemistry.

Fig. 1: An image from C3Headlines; the 3 C's are "Climate, Conservative, Consumer". Oh, and the article is titled "The Left/Liberal Bizarro, Anti-Science Hyperbole Continues". It sure would be tragic if they made obvious n00b mistakes after using such language. Click for link!

Coming from an article on the website C3Headlines, this image claims that carbon dioxide concentrations have ‘Linear, Not Exponential Growth’. thereby ‘expos[ing] the lunacy of typical left/liberal/progressive/Democrat anti-science’, The author has reached this conclusion by graphing January CO2 levels* and fitting a linear trendline to them.

Already this is a warning sign – the comparisons the author makes are entirely qualitative, apparently  based up on eyeballing the graph. However, trend lines are created by a statistical process called a linear regression, which comes with a caveat: it will fit a trend line to ANY data given to it, linear or nonlinear. Fortunately, there are also ways of evaluating how good a trend line is. Continue reading

temperature aNOMalies

If you are new to climate science, you might be wondering what, exactly, this ‘temperature anomaly’ thing is that you keep hearing about. I know I was a bit confused at first! This post explains the concept, using a real-world example.

Absolute temperatures (yearly averaged) from two sites in the UK: one urban (St. James Park, green) and one rural (Rothamsted, red). Although the urban site is consistently warmer, the two sites show the same warming trend. But is there a way to compare them directly? Data from Jones et al. 2008, kindly provided by Dr. Jones.

Cities tend to be warmer than their surrounding countrysides, a fact known as the urban heat island effect (UHI). This occasionally is offered as an alternative explanation for greenhouse warming, but it fails on closer inspection. We can use data from Jones et al. (2008) [PDF] to see one reason UHI can’t explain observed warming. One time series is from St. James Park, in the city of London; the other is from nearby Rothamsted, a rural site some tens of miles away. As you can see, the urban location is consistently about 2 C warmer; however, the warming is nearly identical at both sites (a strongly significant 0.03 deg C/year). Jones et al. note:

“… the evolution of the time series is almost identical. As for trends since 1961 all sites give similar values …  in terms of anomalies from a common base period, all sites would give similar values.”

This gives us a hint about what a temperature anomaly is: Continue reading

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