“It’s a bit like seeing a rabbit shape in the clouds and then testing whether all clouds look like rabbits… using the same cloud. I hope you appreciate that you’re going to need some new clouds to test your theory.
Any datapoint you use to inspire a theory or question can’t be used to test that same theory.”
https://towardsdatascience.com/the-most-powerful-idea-in-data-science-78b9cd451e72