I teach curve fitting with this dataset and recently added the fifth dataset. It illustrates Simpsons paradox.

https://www.linkedin.com/posts/panela_loved-adding-ancombes-...

That's an amazing addition! Once I read about Simpson's paradox[0], couldn't help but seeing it or suspecting it everywhere. Luckily, it is not a true paradox, and it can resolved if underlying data is available and not just summary statistics.

I recommend putting together the Quintet in one image, so that the original 4 charts, plus the new one are all visible and interpretable together. It will be learning aid for decades to come.

[0] https://en.wikipedia.org/wiki/Simpson's_paradox