Not exactly a textbook, but good to read nonetheless is, "Statistics Done Wrong"[1]. It is a short read but is filled with all the most common ways in which statistical analysis is abused with concrete examples.

[1] Statistics Done Wrong: The Woefully Complete Guide https://www.amazon.com/dp/1593276206/ref=cm_sw_r_cp_apa_i_u....

I think the paper as it stands is deficient. As I've mentioned in my previous comment, in the tech sector particularly, compensation is a combination of salary, stocks, bonuses, etc.

Unless it adopts a more rigorous methodology, the paper paints a limited picture. [1]

For example, according to PayScale, Google pays on average $15,030 in annual employee bonuses (anywhere from $1,000 to $80,000), and for comparison, Facebook pays $12,860. These numbers will have a significant effect on hourly compensation.

Unfortunately, statistical analysis is tricky to get right, and plenty of papers contain errors and omissions, and I'm not necessarily saying that's the case here, but one ought to be aware. More on this topic, in case anyone is interested – Statistics Done Wrong [2]

[1] https://www.bls.gov/ncs/ncbr0002.pdf

[2] https://www.amazon.com/gp/product/1593276206