> What I was seeing between Node versions really should have been a bug in the testing library, or something in my code, or maybe in simple-statistics itself.

> What I was seeing between Node versions really should have been a bug in the testing library, or something in my code, or maybe in simple-statistics itself. But in this case, digging deeper revealed that what I was seeing was exactly what you don’t expect: a glitch in the language itself. This is such a disheartening conclusion. It really was a bug in your code, describing it as a "glitch in the language" is disingenuous. Your code was assuming higher level of precision (or accuracy? I get those always mixed) from the system was providing, that is not a glitch in the language, but bug in your code making that false assumption. This also leads to the question where did the original "13098426.039156161" reference value come from? Has he actually verified by hand that it is correct to the last decimal? WolframAlpha gives lot more decimals for the value, how did he decide that exact number of digits? Of course hindsight 20/20, but numerical code just is generally much more difficult and complex than many people give credit to, at least before they get bitten by some issue like the author.