May 28, 2015

More Gallup Misrepresentation. This time, obesity.

Yet another Gallup survey is making the rounds, lately. This one is about obesity by state. This time, instead of quintiles, the accompanying map is, as you can see, split into arbitrary cut-offs of obesity. If you want, you can go over there and look at their map or look at the first map below. It represents the cut-offs in approximately same colors. (If you mouseover the map, you'll get more information by state.)

Obesity by State, Arbitrary Categories
"Squashed" Range
Full Range

This map is an excellent example of how data presentation choices can be fraudulent without being fraudulent, how to lie without lying. Honest people use quintiles, quartiles, percentiles, and other such non-parametric numbers to represent either data that has a long, uneven, and strung-out range (like achievement test scores), or to group a different set of data to show how it is distributed (like wealth per quintile). It just so happens that you can look a the obesity percentages for yourself. Notice that the data is not the strung-out and scattered. In fact, it is very densely-packed. It also is not linked to some other unevenly-distributed data.

The obesity rates are actually very densely packed. From 0% obese to 100% obese, the lowest state's rate is 19%. The highest is 35.2%. Look at that first map, again. Is a difference of about 16 percentage points worth that much a visual difference?

How else to represent the difference so people can get an idea of reality instead of a visual lie that technically represents the actual numbers? The second, or "squashed scale" map does that. The "worst color" (dark gray) is matched to rate of 35.2%. The "best color" is matched to 19%. The range between is then evenly filled in among the three color points. Look different? It does. Yes, there is some rough correspondence between the misleading map that comes from Gallup and the (somewhat) more truthful map I created

But I'm not finished. You see a third map. This is a map where the "worst color" corresponds to 100% obesity in the population (which is the worst possible condition) and the "best color" corresponds to no obesity. Thus, changes in color correspond to linear differences along the full possible range. Having a hard time telling the states apart? That is because the differences among them in this index really are quite small--total range is 16.2 percentage points out of 100. This map shows you what that looks like.

So, why does Gallup do this, and why do people so stupidly and eagerly swallow such dishonest representation of data? First, explaining Gallup. I don't work there, so this is speculation, but Gallup makes its money off turmoil. Anything they publish that will stir the pot will inspire more surveys that they can sell. Likewise, presenting things in extreme (and dishonest) ways ensures that there will be more arguments, leading to more survey commissions, leading to more dishonest data presentation, leading to more arguments. It's a lucrative circle for Gallup.

But why do people so eagerly devour such steaming dog turds of quasi-information? First, they're simple. People like very stark, very simple things to natter on about with each other. People do not like complex and shaded descriptions. They want things to be very neatly pigeonholed, and this comforts them. In addition, people with agendas want things presented as rigidly and extremely as possible to the public, all the better to sound the panic alarm and drum the masses into obedience. Finally, we are taught that only rigid and extreme answers can be "true". We are indoctrinated to be mental weaklings, to always see the world as "good" and "evil" with nothing in between. We are taught that someone who is able to see gradual differences is a "fence-sitter" or "spineless". We are told that only extremism is good--although it's only actually extremism when it's someone you don't like doing it.

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