Eric’s Enlightenment for Thursday, April 30, 2015

  1. Simon Jackman from Stanford University provides some simple examples of obtaining the posterior distribution using conjugate priors.  If you are new to Bayesian statistics and need to develop the intuition for the basic ideas, then work through the math in these examples with pen and paper.
  2. Did you know that there are plastics that conduct electricity?  In fact, Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa won the 2000 Nobel Prize in Chemistry for the work on this fascinating subject.
  3. Jared Niemi provides a nice video introduction of mixed-effects models.  I highly encourage you to work through the math with pen and paper.
  4. Alberto Cairo adds a healthy dose of caution about the recent advent of data-driven journalism.  He emphasizes problems like confusing correlation with causation, ecological fallacies, and drawing conclusions based on small sample sizes or unrepresentative samples.

Discovering Argon with the 2-Sample t-Test

I learned about Lord Rayleigh’s discovery of argon in my 2nd-year analytical chemistry class while reading “Quantitative Chemical Analysis” by Daniel Harris.  (William Ramsay was also responsible for this discovery.)  This is one of my favourite stories in chemistry; it illustrates how diligence in measurement can lead to an elegant and surprising discovery.  I find no evidence that Rayleigh and Ramsay used statistics to confirm their findings; their paper was published 13 years before Gosset published about the t-test.  Thus, I will use a 2-sample t-test in R to confirm their result.

Lord Rayleigh                                    William Ramsay

Photos of Lord Rayleigh and William Ramsay

Source: Wikimedia Commons

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