Ask HN: Detailed data science/engineer challenges?

Do you use a specific hiring challenge or "homework" assignment to evaluate data science/engineer candidates? Can you share examples that would be exciting to you as a hiring manager or member of a team adding a data science/engineer to your team?

My first reason for asking is selfish - I enjoy hacking away at these types of hiring challenges.

My second reason is more pragmatic - as an adjunct lecturer, a number of students I have interacted with are interested in breaking into data science/engineering. I'd like to give them some solid side project ideas plus a sense of "applied" work.

Lastly, have candidates for your positions come in with an impressive portfolio of work independently? Are the candidates heavily credentialed (PhD/MS in CS/Stats/Math)?