He made major contributions to statistics. The Wald test in statistics is named after him (<a href="https://en.wikipedia.org/wiki/Wald_test" rel="nofollow">https://en.wikipedia.org/wiki/Wald_test</a>). I think he was also a forerunner of decision theory and invented an early form of the minimax principle:<p>Wald, A. (1939). Contributions to the theory of statistical estimation and testing hypotheses. The Annals of Mathematics, 10(4), 299-326.
Few weeks of intense reading to understand a whole semester's worth of mathematics... I'd also like to have that skill.<p>Perhaps being homeschooled helped acquire such skill.
The article covers so much -- and it doesn't even mention the "Wald estimator," which is part of the foundation of the modern (causal-inference-oriented) view of the method of instrumental variables.
...died in 1950 aged 48 in a plane crash on an Indian lecture tour.<p>Add to other mathematicians who would have been even more prominent if they hadn't died before their time: Galois, Ramanujan, Turing...
(when following Wald's work on rearranging series)<p>This is a nice riddle:<p>Is summing the series:<p>1, -1, 1, 1,....<p>0 = (1-1)+(1-1)+(1-1)....=0+0+0...<p>or<p>1 = 1+(-1+1)+(-1+1)+(-1+1)....=1+0+0+0...