Eric’s Enlightenment for Friday, May 29, 2015

  1. P2N3: An aromatic ion made of just phosphorous and nitrogen.  (Yes, aromaticity can be entirely inorganic!)
  2. Using 3-D printing and plastics to make prosthetics.
  3. David Beckwroth and Scott Sumner talk at length about reforming monetary policy with NGDP targeting in this video interview/seminar.
  4. Anky Lai gives a nice introduction to PROC TABULATE (PDF document) – an alternative to PROC FREQ and PROC MEANS in SAS.  Check out her awesome code samples for generating nicely formatted tables and exporting them conveniently into spreadsheets in Excel!

Statistics and Chemistry Lesson of the Day – Illustrating Basic Concepts in Experimental Design with the Synthesis of Ammonia

To summarize what we have learned about experimental design in the past few Applied Statistics Lessons of the Day, let’s use an example from physical chemistry to illustrate these basic principles.

Ammonia (NH3) is widely used as a fertilizer in industry.  It is commonly synthesized by the Haber process, which involves a reaction between hydrogen gas and nitrogen gas.

N2 + 3 H2 → 2 NH3   (ΔH = −92.4 kJ·mol−1)

Recall that ΔH is the change in enthalpy.  Under constant pressure (which is the case for most chemical reactions), ΔH is the heat absorbed or released by the system.

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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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