Friday, November 20, 2015

Corrected Polling Numbers

A few weeks ago I posted a fairly hefty critique of a survey conducted by Fort Hays State University researchers on the political climate in Kansas.  The survey claimed a lot of things, but the issue receiving the most press was that Kansas Governor Brownback had an 18% approval rate.  I took issue with that number for various reasons, largely due demographic skews in the data, hinting at sampling or response bias.


Sometime later a twitter user asked me, if not 18%, what do I really think Brownback's approval rating might be.  I looked again at the skews, did some quick math, adjusting for prior demographic distributions and likely errors and came up with a range.  This was me really just trying to back into a number from bad polling data.  Here's my response on twitter:


This week another survey was published that reviews the approval rate of all governors in the US.  You can find that study here.  I haven't fully vetted the methodology, but the methodology indicates they at least tried to deal with demographic issues.

What did that study tell us?
Brownback's approval rate is 26%.  LOOK THAT'S IN MY RANGE!
But that dataset also provides information on other governor approval ratings, what can those tell us?


While I was correct that Brownback's likely approval rate is above 18%, his approval rate is still dismal compared to other governors.  In fact Brownback is 9 percentage points below any other governor, and a huge outlier.  I could bore you with p-values and z-scores (-2.8) and other statistical nerdery, but two charts can easily describe how bad his approval rate is. (Brownback in red)


Takeaways bullets:
  • Brownback's approval rate is likely above 18%, closer to 26% (read: I was right).
  • Brownback has the lowest approval rate among US governors.
  • Brownback's approval rating is an extreme low outlier.  

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