One on a highly-used but lesser-known statistical test:

https://www.jwilber.me/permutationtest/

Thank you! I was not aware of permutation tests and this was a very accessible explanation with great visuals.

Does anybody know of resources like this for other mathematics topics?

Explorable Explanations: https://explorabl.es/

Interactive Machine Learning, Deep Learning and Statistics websites: https://p.migdal.pl/interactive-machine-learning-list/

Here's some interactive mathematical gizmos: https://www.tungsteno.io/

If curious see also

2018 https://news.ycombinator.com/item?id=18769099

2017 https://news.ycombinator.com/item?id=13760353

2017 https://news.ycombinator.com/item?id=13735714

404 on the feedback page.

Typo on page 9:

A =. {first flip heads} = {HH, HT}

B =. {second flip heads} = {HT, TT}