On citing common knowledge and giving credit to the 'right' authors Suppose that I am reading a marketing book and, while reading a specific chapter, I find like there are 10 footnotes with most of them related to specific examples or specific numbers; in other words, most of the information presented in the chapter are not cited and, judging by the context and contents, such information do not appear to be 'invented' by the author(s) of the book (not primary data). In that case, they could just be common knowledge information related to the field of marketing and business (example: purpose of marketing, strategic analysis, financial measures, etc...)

Since 'when in doubt, always cite', if I want to write about information taken from such book, is it bad if I just cite the author(s) of the book since I am taken the information from their book? To clarify, I am worried that I could be 'giving credit' to people who did NOT come up with such information presented in their book and therefore, I should not cite since it's common knowledge or whatever.
First, the definition of "common knowledge" and I think this answer by Ben Norris from the post that Stephan Branczyk posted elucidated that pretty well (https://academia.stackexchange.com/a/2196):


  If the statement/concept/idea that you think you want to cite is covered (without citation) in the introductory undergraduate textbook(s) on the subject, then it is likely common knowledge in the field.  


So next step is to search more than one sources about that specific examples or specific numbers. If that book is the only source that came up with that example/number then you can cite from that author(s). You give credit from where you found the information. It is better to cite than not and might trouble you later on since it will give an impression that those numbers/examples are from your own findings (and which someone might cite that example from you). Because again, 'when in doubt, always cite'.