My Casio FX-260 Solar IIs [1][2] (I recently bought 3 more of them) cost me $5 CAD a piece on clearance at Walmart. No battery, a modern solar panel that works great even in dimly lit rooms, and a modern SOC with all the standard scientific calculations, scientific notation, engineering notation, significant figures, and all the basic stats calculations too (sum, mean, pop stddev, sample stddev, permutations, combinations, factorials).

It’s my favourite calculator and the one I always reach for, despite having a bunch of more complicated 2-line calculators etc. It’s just so easy to use and very fast to do anything I’d want with a calculator. If I need graphing I’ll reach for Desmos. If I need algebra I’ll use Sage. I haven’t used Sage since my undergrad, however.

[1] https://www.casio.com/content/dam/casio/product-info/locales...

[2] https://www.casio.com/ca-en/scientific-calculators/product.F...

The basic $12 Casio scientific has stats like mean, standard deviation, regression... Stats is a huge field, we're talking highschool level. I think it probably covers it

HL or SL? (It's been a while for me, but I know I needed PDF/CDF functions... and I don't know about the optional modules/Further.)