Statistical functions for use in data analysis

Relevant project
Thanks to the courses on here, I have been working to develop a portfolio in the hopes of becoming a data analyst.
After reviewing the functions in scipy.stats, NumPy, etc, as well as reviewing statistics on khan academy, I noticed several hypothesis tests as well as a few other things (namely finding confidence intervals for a given sample proportion or mean) did not seem to be there. So I made an attempt to define some for myself.
I have tested these to make sure they are giving appropriate answers and results. I would love some feedback and suggestions for the code themselves (especially how to better write them to be used in datasets). In addition, if any stats experienced folk come across this, please let me know if you see any issues with the formulas as I have put them down here.
Thanks so much!