Anyone knows a good book to learn about that subject? I don't know shit about that but I really want to learn.
From an abstract perspective, Nate Silver of FiveThirtyEight has an incredible book on how humans interpret complex datasets. I love this book, it's so easy to pick up and read. Thinking about making it required reading for my design interns.
You should check out Google's HEART framework, it is pretty straight forward.
Here is a medium article and below is the study.
I would also pair this with a hypothesis driven design approach to maintain integrity in your process.
The entire "LEAN" series - Lean Startup, Lean UX, UX for Lean Startups, and Lean Analytics - is excellent. I found UX for Lean Startups to be especially helpful, as Laura Klein's method of writing and presenting ideas is clear and actionable. I would also recommend her blog.
These books present the full story from idea validation, iterating through experimentation, and constantly testing your design through metrics analysis. It's useful even outside the Lean paradigm.
Quantifying the user experience is great too.
I've also bookmarked a few articles. None is exhaustive, but they offer some good starting points and Google keywords:
If this is something you really want to get better at, reach out to product managers or other designers at your company or through Twitter, etc who would be willing to mentor you on your process, help you design experiments, and hone your skills.