I'm trying to learn about A/B testing with more statistical depth. I have a good idea of the basics, however, I am struggling to find decent resources that discuss all the mathematical technicalities and properly prove formulas and methodology. I've been jumping between youtube videos and suggested industry books, but none have provided the depth I'm looking for and some give different or contradicting information on the details.
I'm wondering if anyone could suggest some reliable free resources that discuss A/B testing in full statistical depth, or if anyone is willing to do a full breakdown of the topic. If there are any suggestions on how I can better learn the material, I'd appreciate it.